JP2023047706A - Filter generation device and filter generation method - Google Patents

Abstract

To provide a filter generation device and filter generation method capable of generating a filter suitable for out-of-head localization processing.SOLUTION: A processing device comprises: a frequency characteristic acquisition section for acquiring frequency characteristics based on a sound collection signal; a level calculation section for calculating a reference level in the frequency characteristics; a correction section 225 for calculating correction characteristics by correcting the frequency characteristics to be within a predetermined level range including the reference level; and a filter generation section 230 for generating a correction filter based on the correction characteristics.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to a filter generation device and a filter generation method.

As a sound image localization technique, there is an out-of-head localization technique in which a sound image is localized outside the listener's head using headphones. In the out-of-head localization technology, the characteristics from the headphones to the ears (headphone characteristics) are canceled, and the characteristics of the two channels from one speaker (monaural speaker) to the ears (spatial acoustic transfer characteristics) are given to the sound image out of the head. is positioned at

In the out-of-head localization reproduction of stereo speakers, a measurement signal (impulse sound, etc.) emitted from two-channel (hereinafter referred to as ch) speakers is transmitted to a microphone (hereinafter referred to as a microphone) placed in the ear of the listener (listener). ). Then, the processing device generates a filter based on the collected sound signal obtained by collecting the measurement signal. Out-of-head localization reproduction can be realized by convolving the generated filter with the 2ch audio signal.

Furthermore, in order to generate a filter (also called an inverse filter) that cancels the characteristics from the headphone to the ear, the characteristics from the headphone to the ear to the eardrum (external auditory transfer function ECTF, also called the external auditory canal transfer characteristic) is applied to the listener's own ear. Measure with a microphone placed on the

Patent Document 1 discloses an apparatus for performing out-of-head localization processing. Furthermore, in Patent Document 1, out-of-head localization processing performs DRC (Dynamic Range Compression) processing on a reproduced signal. In the DRC processing, the processing device smoothes the frequency characteristics. Further, a processor performs band division based on the smoothed characteristics.

JP 2019-62430 A

In such out-of-head localization listening, it is desirable to perform processing without being limited to a specific playback device. For example, even when the user uses headphones as the playback device, it is desirable to appropriately perform out-of-head localization processing. Alternatively, it is desired to reproduce the spatial sound transfer characteristics in an environment where the speaker that the user normally uses is installed as a reproduction device.

If the playback equipment is changed, the transfer characteristics may change. Therefore, it is preferable to measure the user's individual characteristics (spatial sound transfer characteristics and ear canal transfer characteristics) using the playback equipment that the user uses. Even when the individual characteristics are measured, sharp peaks and dips occur in the frequency characteristics, which may cause the out-of-head localization-processed signal to clip.

Peaks and dips change depending on the characteristics of playback equipment such as speakers and headphones, or the acoustic characteristics of the room that is the measurement environment. The peaks and dips also change depending on the shape of the user's head and ears. Therefore, the levels and frequencies of peaks and dips change due to various causes. Depending on the playback device, the measurement environment, etc., it becomes necessary to check the characteristics and make adjustments according to the playback device, the measurement environment, and the like.

The present disclosure has been made in view of the above points, and aims to provide a filter generation device and a filter generation method capable of generating a filter suitable for out-of-head localization processing.

A filter generation device according to the present embodiment includes a frequency characteristic acquisition unit that acquires frequency characteristics based on a picked-up sound signal, a level calculation unit that calculates a reference level in the frequency characteristics, and a predetermined level including the reference level. A correction unit that calculates a correction characteristic by correcting the frequency characteristic so as to fall within a level range, and a filter generation unit that generates a correction filter based on the correction characteristic.

A filter generation method s according to the present embodiment includes the steps of obtaining a frequency characteristic based on a picked-up sound signal, calculating a reference level in the frequency characteristic, and adjusting the a step of calculating a correction characteristic by correcting the frequency characteristic; and a step of generating a filter based on the correction characteristic.

According to the present disclosure, it is possible to provide a filter generation device and a filter generation method capable of generating a filter suitable for out-of-head localization processing.

1 is a block diagram showing an out-of-head localization processing apparatus according to this embodiment; FIG. It is a figure which shows typically the structure of the measuring apparatus which measures a spatial sound transfer characteristic. It is a figure which shows typically the structure of the measuring device which measures an external auditory canal transfer characteristic. It is a control block diagram which shows the structure of a processing apparatus. It is a flowchart which shows the filter generation method in a processing apparatus. 5 is a flowchart showing a processing example 1 of correction processing; 7 is a graph showing frequency-amplitude characteristics before and after correction according to Processing Example 1; 10 is a flowchart showing a processing example 2 of correction processing; 10 is a graph showing frequency-amplitude characteristics before and after correction by Processing Example 2; FIG. 11 is a flowchart showing a processing example 4 of correction processing; FIG. 10 is a graph showing frequency bands according to Processing Example 4; 2 is a block diagram showing the configuration of a processing device according to a second embodiment; FIG.

An overview of sound image localization processing according to the present embodiment will be described. The out-of-head localization processing according to the present embodiment uses the spatial sound transfer characteristics and the ear canal transfer characteristics to perform the out-of-head localization processing. Spatial sound transfer characteristics are transfer characteristics from a sound source such as a speaker to the ear canal. The ear canal transfer characteristic is the transfer characteristic from the speaker unit of the headphone or earphone to the eardrum. In the present embodiment, the spatial sound transfer characteristics are measured without wearing headphones or earphones, and the ear canal transfer characteristics are measured with headphones or earphones worn, and these measurement data are used. Out-of-head localization processing is realized. This embodiment is characterized by a microphone system for measuring spatial sound transfer characteristics or ear canal transfer characteristics.

The out-of-head localization processing according to this embodiment is executed by a user terminal such as a personal computer, a smart phone, or a tablet PC. A user terminal is an information processing device having processing means such as a processor, storage means such as a memory and a hard disk, display means such as a liquid crystal monitor, and input means such as a touch panel, buttons, keyboard, and mouse. A user terminal may have a communication function for transmitting and receiving data. Furthermore, output means (output unit) having headphones or earphones are connected to the user terminal. The connection between the user terminal and the output means may be wired connection or wireless connection.

Embodiment 1.
(Out-of-head stereotactic processing device)
FIG. 1 shows a block diagram of an out-of-head localization processing device 100, which is an example of a sound field reproducing device according to this embodiment. The out-of-head localization processing device 100 reproduces a sound field for the user U wearing the headphones 43 . Therefore, the out-of-head localization processing apparatus 100 performs sound image localization processing on the Lch and Rch stereo input signals XL and XR. The Lch and Rch stereo input signals XL and XR are analog audio reproduction signals output from a CD (Compact Disc) player or the like, or digital audio data such as mp3 (MPEG Audio Layer-3). Note that the audio reproduction signal or digital audio data will be collectively referred to as a reproduction signal. That is, the Lch and Rch stereo input signals XL and XR are reproduced signals.

It should be noted that the out-of-head localization processing apparatus 100 is not limited to a physically single apparatus, and part of the processing may be performed by a different apparatus. For example, part of the processing may be performed by a smart phone or the like, and the rest of the processing may be performed by a DSP (Digital Signal Processor) built into the headphones 43 or the like.

The out-of-head localization processing device 100 includes an out-of-head localization processing unit 10 , a filter unit 41 that stores an inverse filter Linv, a filter unit 42 that stores an inverse filter Rinv, and headphones 43 . The out-of-head localization processing unit 10, filter unit 41, and filter unit 42 can be specifically realized by a processor or the like.

The out-of-head localization processing unit 10 includes convolution calculation units 11 to 12 and 21 to 22 and adders 24 and 25 that store the spatial sound transfer characteristics Hls, Hlo, Hro and Hrs. The convolution calculation units 11 to 12 and 21 to 22 perform convolution processing using spatial acoustic transfer characteristics. Stereo input signals XL and XR from a CD player or the like are input to the out-of-head localization processing unit 10 . Spatial sound transfer characteristics are set in the out-of-head localization processing unit 10 . The out-of-head localization processing unit 10 convolves a spatial acoustic transfer characteristic filter (hereinafter also referred to as a spatial acoustic filter) to the stereo input signals XL and XR of each channel. The spatial sound transfer characteristic may be a head-related transfer function HRTF measured on the head or pinna of the person to be measured, or may be a head-related transfer function of a dummy head or a third party.

A set of four spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs is defined as a spatial acoustic transfer function. The data used for convolution in the convolution calculation units 11, 12, 21, and 22 serve as spatial acoustic filters. A spatial acoustic filter is generated by cutting out the spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs with a predetermined filter length.

Spatial sound transfer characteristics Hls, Hlo, Hro, and Hrs are obtained in advance by impulse response measurement or the like. For example, the user U wears microphones on the left and right ears, respectively. The left and right speakers placed in front of the user U respectively output impulse sounds for impulse response measurement. Then, a measurement signal such as an impulse sound output from the speaker is picked up by a microphone. Spatial sound transfer characteristics Hls, Hlo, Hro, and Hrs are obtained based on the signals picked up by the microphones. Spatial sound transfer characteristics Hls between the left speaker and the left microphone, Spatial sound transfer characteristics Hlo between the left speaker and the right microphone, Spatial sound transfer characteristics Hro between the right speaker and the left microphone, Right speaker and the right microphone The spatial sound transfer characteristic Hrs between is measured.

Then, the convolution calculation unit 11 convolves the Lch stereo input signal XL with a spatial acoustic filter corresponding to the spatial acoustic transfer characteristic Hls. The convolution calculation unit 11 outputs the convolution calculation data to the adder 24 . The convolution calculation unit 21 convolves a spatial acoustic filter corresponding to the spatial acoustic transfer characteristic Hro with respect to the Rch stereo input signal XR. The convolution calculation unit 21 outputs convolution calculation data to the adder 24 . The adder 24 adds the two pieces of convolution operation data and outputs the result to the filter section 41 .

The convolution calculation unit 12 convolves the Lch stereo input signal XL with a spatial acoustic filter corresponding to the spatial acoustic transfer characteristic Hlo. The convolution calculation unit 12 outputs the convolution calculation data to the adder 25 . The convolution calculation unit 22 convolves a spatial acoustic filter corresponding to the spatial acoustic transfer characteristic Hrs with respect to the Rch stereo input signal XR. The convolution calculation unit 22 outputs the convolution calculation data to the adder 25 . The adder 25 adds the two pieces of convolution operation data and outputs the result to the filter section 42 .

Inverse filters Linv and Rinv for canceling headphone characteristics (characteristics between the reproduction unit of the headphones and the microphone) are set in the filter units 41 and 42 . Inverse filters Linv and Rinv are then convolved with the reproduced signal (convolution calculation signal) processed by the out-of-head localization processing unit 10 . In the filter unit 41, the Lch signal from the adder 24 is convoluted with an inverse filter Linv of headphone characteristics on the Lch side. Similarly, the filter unit 42 convolves the Rch signal from the adder 25 with an inverse filter Rinv of headphone characteristics on the Rch side. The inverse filters Linv and Rinv cancel the characteristics from the headphone unit to the microphone when the headphones 43 are worn. The microphone can be placed anywhere between the ear canal entrance and the eardrum.

Filter section 41 outputs processed Lch signal YL to left unit 43L of headphone 43 . The filter section 42 outputs the processed Rch signal YR to the right unit 43R of the headphone 43 . A user U wears headphones 43 . The headphone 43 outputs to the user U the Lch signal YL and the Rch signal YR (hereinafter, the Lch signal YL and the Rch signal YR are collectively referred to as a stereo signal). Thereby, a sound image localized outside the head of the user U can be reproduced.

In this manner, the out-of-head localization processing apparatus 100 performs out-of-head localization processing using the spatial acoustic filters corresponding to the spatial sound transfer characteristics Hls, Hlo, Hro, and Hrs and the inverse filters Linv and Rinv of the headphone characteristics. there is In the following description, the spatial acoustic filters corresponding to the spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs and the inverse filters Linv and Rinv of the headphone characteristics are collectively referred to as an out-of-head localization processing filter. In the case of a 2ch stereo reproduction signal, the out-of-head localization filter is composed of four spatial acoustic filters and two inverse filters. Then, the out-of-head localization processing apparatus 100 performs out-of-head localization processing by performing a convolution operation on the stereo reproduction signal using a total of six out-of-head localization filters. The out-of-head localization filter is preferably based on user U's individual measurements. For example, an out-of-head localization filter is set based on a sound signal picked up by a microphone attached to the user's U ear.

In this manner, the spatial acoustic filter and the headphone characteristic inverse filters Linv and Rinv are filters for audio signals. By convolving these filters with the reproduced signals (stereo input signals XL and XR), the out-of-head localization processing apparatus 100 executes out-of-head localization processing. One of the technical features of this embodiment is the process of generating a spatial acoustic filter. Specifically, in the process of generating the spatial acoustic filter, level range compression of frequency characteristics is applied.

(Equipment for measuring spatial sound transfer characteristics)
A measuring device 200 for measuring spatial sound transfer characteristics Hls, Hlo, Hro, and Hrs will be described with reference to FIG. FIG. 2 is a diagram schematically showing a measurement configuration for measuring the person 1 to be measured. Here, the person to be measured 1 is the same person as the user U in FIG. 1, but may be a different person.

As shown in FIG. 2 , the measuring device 200 has stereo speakers 5 and a microphone unit 2 . A stereo speaker 5 is installed in the measurement environment. The measurement environment may be a room in the user U's home, an audio system store, a showroom, or the like. The measurement environment is preferably a listening room equipped with speakers and acoustics.

In this embodiment, the processing device 201 of the measurement device 200 performs arithmetic processing for appropriately generating the spatial acoustic filter. The processing device 201 has, for example, a music player such as a CD player. The processing device 201 may be a personal computer (PC), tablet terminal, smart phone, or the like. Alternatively, the processing device 201 may be the server device itself.

The stereo speaker 5 has a left speaker 5L and a right speaker 5R. For example, a left speaker 5L and a right speaker 5R are installed in front of the person 1 to be measured. The left speaker 5L and the right speaker 5R output impulse sounds and the like for impulse response measurement. In the following description of the present embodiment, the number of speakers serving as sound sources is two (stereo speakers), but the number of sound sources used for measurement is not limited to two, and may be one or more. That is, the present embodiment can be similarly applied in a so-called multi-channel environment such as 1ch monaural, 5.1ch, 7.1ch, and the like.

The microphone unit 2 is a stereo microphone having a left microphone 2L and a right microphone 2R. The left microphone 2L is installed on the subject's 1 left ear 9L, and the right microphone 2R is installed on the subject's 1 right ear 9R. Specifically, it is preferable to install the microphones 2L and 2R at positions from the entrance of the ear canal of the left ear 9L and the right ear 9R to the eardrum. The microphones 2L and 2R pick up the measurement signal output from the stereo speaker 5 to acquire the picked-up sound signal. The microphones 2L and 2R output picked-up sound signals to the processing device 201. FIG. The person 1 to be measured may be a person or a dummy head. That is, in the present embodiment, the person to be measured 1 is a concept that includes not only a person but also a dummy head.

As described above, the impulse responses are measured by measuring the impulse sounds output from the left speaker 5L and the right speaker 5R with the microphones 2L and 2R. The processing device 201 stores the picked-up sound signal obtained by the impulse response measurement in a memory or the like. As a result, spatial sound transfer characteristics Hls between the left speaker 5L and the left microphone 2L, spatial sound transfer characteristics Hlo between the left speaker 5L and the right microphone 2R, and spatial sound between the right speaker 5R and the left microphone 2L A transfer characteristic Hro and a spatial sound transfer characteristic Hrs between the right speaker 5R and the right microphone 2R are measured. That is, the spatial sound transfer characteristic Hls is acquired by the left microphone 2L picking up the measurement signal output from the left speaker 5L. The spatial sound transfer characteristic Hlo is acquired by the right microphone 2R picking up the measurement signal output from the left speaker 5L. The spatial sound transfer characteristic Hro is acquired by the left microphone 2L picking up the measurement signal output from the right speaker 5R. The spatial sound transfer characteristic Hrs is acquired by the right microphone 2R picking up the measurement signal output from the right speaker 5R.

In addition, the measuring device 200 generates spatial acoustic filters corresponding to the spatial acoustic transfer characteristics Hls, Hlo, Hro, Hrs from the left and right speakers 5L, 5R to the left and right microphones 2L, 2R based on the collected sound signals. good too. For example, the processing device 201 cuts out the spatial sound transfer characteristics Hls, Hlo, Hro, Hrs with a predetermined filter length. The processing unit 201 may correct the measured spatial sound transfer characteristics Hls, Hlo, Hro, Hrs.

By doing so, the processing device 201 generates a spatial acoustic filter used in the convolution operation of the out-of-head localization processing device 100 . As shown in FIG. 1, the out-of-head localization processing device 100 includes spatial acoustic filters corresponding to spatial acoustic transfer characteristics Hls, Hlo, Hro, Hrs between the left and right speakers 5L, 5R and the left and right microphones 2L, 2R. is used to perform out-of-head localization processing. That is, out-of-head localization processing is performed by convolving the spatial acoustic filter with the audio reproduction signal.

The processing device 201 performs similar processing on the collected sound signals corresponding to the spatial sound transfer characteristics Hls, Hlo, Hro, and Hrs. That is, the same processing is performed for each of the four picked-up sound signals corresponding to the spatial sound transfer characteristics Hls, Hlo, Hro, and Hrs. Thereby, spatial acoustic filters corresponding to the spatial acoustic transfer characteristics Hls, Hlo, Hro, and Hrs can be generated.

(Device for measuring ear canal transfer characteristics)
An ear canal transfer characteristic measuring device 300 will be described with reference to FIG. FIG. 3 shows a configuration for measuring transfer characteristics for user U. In FIG. The measurement device 300 measures ear canal transfer characteristics to generate an inverse filter. The measuring device 300 includes a microphone unit 2 , headphones 43 and a processing device 301 . Here, the person to be measured 1 is the same person as the user U in FIG. 1, but may be a different person.

In this embodiment, the processing device 301 of the measuring device 300 performs arithmetic processing for appropriately generating filters according to the measurement results. The processing device 301 is a personal computer (PC), tablet terminal, smart phone, or the like, and includes a memory and a processor. The memory stores processing programs, various parameters, measurement data, and the like. The processor executes a processing program stored in memory. Each process is executed by the processor executing the processing program. The processor may be, for example, a CPU (Central Processing Unit), FPGA (Field-Programmable Gate Array), DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), or GPU (Graphics Processing Unit). .

Further, the processing device 301 in FIG. 3 may be physically the same processing device as the processing device 301 in FIG. 2, or may be a different processing device. That is, the measurements of FIGS. 2 and 3 are not limited to configurations performed using the same processing apparatus. For example, the measurement shown in FIG. 2 may be performed by a dedicated measurement processing device 201 installed in a squirrel ring room, and the measurement shown in FIG. 3 may be performed by a general-purpose processing device 301 such as a smart phone.

A microphone unit 2 and a headphone 43 are connected to the processing device 301 . Note that the microphone unit 2 may be built in the headphone 43 . The microphone unit 2 has a left microphone 2L and a right microphone 2R. The left microphone 2L is worn on the user's U left ear 9L. The right microphone 2R is worn on the user's U right ear 9R. The processing device 301 may be the same processing device as the out-of-head localization processing device 100, or may be a different processing device. It is also possible to use earphones instead of the headphones 43 .

The headphone 43 has a headphone band 43B, a left unit 43L, and a right unit 43R. Headphone band 43B connects left unit 43L and right unit 43R. The left unit 43L outputs sound toward the user's U left ear 9L. The right unit 43R outputs sound toward the user's U right ear 9R. The headphone 43 may be closed type, open type, semi-open type, semi-closed type, or the like, regardless of the type of headphone. The user U wears the headphones 43 while the microphone unit 2 is worn by the user U. That is, the left ear 9L and the right ear 9R to which the left microphone 2L and the right microphone 2R are attached are respectively attached with the left unit 43L and the right unit 43R of the headphone 43 . The headphone band 43B generates an urging force that presses the left unit 43L and the right unit 43R against the left ear 9L and the right ear 9R, respectively.

The left microphone 2L picks up sound output from the left unit 43L of the headphone 43. FIG. The right microphone 2R picks up sound output from the right unit 43R of the headphone 43. FIG. The microphone parts of the left microphone 2L and the right microphone 2R are arranged at sound pickup positions near the outer ear canal. The left microphone 2L and the right microphone 2R are configured so as not to interfere with the headphone 43. FIG. That is, the user U can wear the headphones 43 with the left microphone 2L and the right microphone 2R arranged at appropriate positions on the left ear 9L and the right ear 9R.

The processing device 301 outputs measurement signals to the headphones 43 . As a result, the headphone 43 generates an impulse sound or the like. Specifically, the impulse sound output from the left unit 43L is measured by the left microphone 2L. The impulse sound output from the right unit 43R is measured by the right microphone 2R. When the measurement signal is output, the microphones 2L and 2R acquire the picked-up sound signal to perform the impulse response measurement.

The processing device 301 generates inverse filters Linv and Rinv by performing similar processing on the sound signals picked up from the microphones 2L and 2R.

(Level range compression)
At least one of the measurement devices 200 and 300 performs range compression processing so that the frequency characteristics of the collected sound signal fall within a predetermined level range. In the following description, the process of compressing the level range of the frequency characteristics of the collected sound signal corresponding to the spatial sound transfer characteristics Hls and Hlo in the measuring device 200 will be described. That is, in the measuring apparatus 200, the processing for compressing the level range of the frequency characteristics of the picked-up sound signals corresponding to the spatial sound transfer characteristics Hro and Hrs is the same as the processing described below, so description thereof will be omitted as appropriate. Similarly, the process of compressing the level range of the frequency characteristic of the collected sound signal with respect to the left and right ear canal transfer characteristics in the measuring apparatus 300 is the same as the process described below, and thus description thereof will be omitted as appropriate.

4 is a block diagram showing the configuration of the processing device 201 of the measuring device 200. As shown in FIG. The processing device 201 includes a measurement signal generation unit 211, a collected sound signal acquisition unit 212, a segmental power acquisition unit 215, a frequency characteristic acquisition unit 221, a level calculation unit 223, a level range setting unit 224, and a correction unit. 225 , an adjustment unit 231 and an inverse transform unit 232 . The inverse transforming section 232 and the adjusting section 231 function as the filter generating section 230 .

The measurement signal generator 211 includes a D/A converter, an amplifier, and the like, and generates a measurement signal for measuring spatial sound transfer characteristics and ear canal transfer characteristics. The measurement signal is, for example, an impulse signal, a TSP (Time Stretched Pulse) signal, or the like. Here, the measurement device 200 performs impulse response measurement using impulse sound as the measurement signal. The measurement signal generator 211 outputs the measurement signals to the stereo speakers 5, respectively. Here, an example in which a measurement signal is output from the left speaker 5L in order to acquire a collected sound signal corresponding to the spatial sound transfer characteristics Hls and Hlo will be described.

The left microphone 2L and the right microphone 2R of the microphone unit 2 each pick up the measurement signal and output the picked-up sound signal to the processing device 201 . The collected sound signal acquisition unit 212 acquires the collected sound signals picked up by the left microphone 2L and the right microphone 2R. The collected sound signal acquisition unit 212 may include an A/D converter that A/D converts the collected sound signals from the microphones 2L and 2R. The collected sound signal acquisition unit 212 cuts out the collected sound signal at a predetermined time. That is, the collected sound signal acquisition unit 212 extracts a preset number of data (time width) of collected sound signals. The collected sound signal acquisition unit 212 may synchronously add signals obtained by multiple measurements. The collected sound signal obtained using the left microphone 2L is defined as hls, and the collected sound signal obtained using the right microphone 2R is defined as the collected sound signal hlo. The collected sound signals hls and hlo are signals sampled at a sampling frequency of 48 kHz. Also, the collected sound signals hls and hlo after clipping are each filtered with a filter length (the number of samples) of 4096. FIG. Of course, the sampling frequency and filter length are not limited to the above values.

The segmental power acquisition unit 215 acquires segmental powers of the collected sound signal hls and the collected sound signal hlo. For example, the segmental powers of the collected sound signal hls and the collected sound signal hlo are hlsP and hloP. The segmental power hlsP is the sum of squares of the amplitude values contained in the picked-up sound signal hls. The segmental power hloP is the sum of squares of the amplitude values contained in the collected sound signal hlo. In the time domain, if the collected sound signal hls and the collected sound signal hlo have 4096 data, the sum of the squares of the 4096 amplitude values becomes the segmental powers hlsP and hloP.

The frequency characteristic acquisition unit 221 acquires frequency characteristics based on the collected sound signals hls and hlo. The frequency characteristic acquisition unit 221 calculates frequency characteristics of the collected sound signals hls and hlo by discrete Fourier transform and discrete cosine transform. The frequency characteristic acquisition unit 221 calculates the frequency characteristic by, for example, performing FFT (Fast Fourier Transform) on the collected sound signal in the time domain. A frequency characteristic includes an amplitude spectrum and a phase spectrum. Note that the frequency characteristic acquisition unit 221 may generate a power spectrum instead of the amplitude spectrum. Let Fhls and Fhlo be the frequency-amplitude characteristics of the collected sound signals hls and hlo, respectively. The frequency characteristics Fhls and Fhlo are spectrum data of the amplitude spectrum.

The level calculator 223 calculates reference levels in the frequency characteristics Fhls and Fhlo. For example, the level calculator 223 calculates the average level (average value) of the frequency characteristics Fhls and Fhlo and uses it as the reference level. For example, if FFT is performed with a filter length (the number of samples) T, the level value (dB) of each frequency of the frequency-amplitude characteristic is calculated and the average value is obtained. Let real (real part) and imag (imaginary part) after T-point FFT be real[i] and imag[i], respectively. Here, i is an integer from 0 to (T-1). The sound pressure level Amp_dB[i] at each i point is given by the following equation (1).
Amp_dB[i]=log10(sqrt(real[i]*real[i]+imag[i]*imag[i])) (1)
In equation (1), i=1 to (T/2+1) and sqrt is the square root.

Further, when the frequency (Hz) at the i point is freq[i] and the sampling frequency is fs, freq[i] is obtained by the following equation (2).
freq[i]=(T/fs)*i (2)

A reference level A in the entire frequency band is obtained by the following equation (3).

Assuming that the reference level of the frequency characteristic Fhls is Ahls and the reference level of the frequency characteristic Fhlo is Ahlo, the reference level A is (Ahls+Ahlo)/2.

Further, the level calculator 223 calculates the maximum level maxL and the minimum level minL of the frequency-amplitude characteristic. The maximum level maxL is the maximum value among the amplitude values included in the two spectrum data of the frequency characteristics Fhls and Fhlo. The minimum level minL is the minimum value among the amplitude values included in the two spectrum data of the frequency characteristics Fhls and Fhlo. The reference level A, the maximum level maxL, and the minimum level minL are common values for the two frequency characteristics Fhls and Fhlo.

A level range setting unit 224 sets a level range X for compression. The level range setting unit 224 inputs the level range X according to, for example, the playback device. In order to obtain an appropriate out-of-head localization effect, it is preferable to set X=40 dB or more. In addition, when the amplifier of the playback device is not high performance such as efficiency and quality of audio output, X=20 dB can also be used. Although it is preferable that X=20 dB or more and 40 dB or less, X is not particularly limited to this range.

The correction unit 225 calculates a correction characteristic by correcting the frequency characteristics Fhls and Fhlo so that the frequency characteristics fall within a predetermined level range X including the reference level A. FIG. That is, the correction unit 225 compresses the frequency characteristics Fhls and Fhlo amplitude levels so that the amplitude values of the frequency characteristics are included in the level range X. FIG. For example, when the level range X=40 dB, the correction unit 225 corrects the frequency characteristics Fhls and Fhlo by compressing the amplitude value so that it falls within the range of the reference level A±20 dB. The characteristics corrected by the correction unit 225 are defined as corrected characteristics. Let NewFhls be the correction characteristic for the frequency characteristic Fhls, and NewFhlo be the correction characteristic for the frequency characteristic Fhlo.

Let L be the amplitude value before correction at an arbitrary frequency, and NewL be the amplitude value after correction. That is, the frequency characteristics Fhls and Fhlo are a set of amplitude values L before correction, and the corrected characteristics NewFhls and NewFhlo are a set of amplitude values NewL.

For example, the correction unit 225 can correct the frequency characteristic using the following equations (4) and (5).
NewL=A+(L−X)*(X/2)/(maxL−A) (4) when L is greater than or equal to A
If L is less than A, NewL=A+(L−X)*(X/2)/(A−minL) (5)

By doing so, NewL comes to fall within the level range X centered on the reference level. That is, NewL has an amplitude value equal to or greater than (A-(X/2)) and equal to or less than (A+(X/2)). Then, the correction unit 225 calculates the post-correction amplitude value NewL for all the data (amplitude value L) within the correction band using the above equations (1) and (2). A set of amplitude values NewL after correction becomes a correction characteristic. A correction characteristic is obtained by correcting the amplitude value of the frequency characteristic Fhls. Further, by correcting using (1) and (2), the range can be compressed while maintaining the spectral shapes of the frequency characteristics Fhls and Fhlo before correction.

Note that the frequency band corrected by the correction unit 225 may be the entire band or a part of the band. For example, the correction band for correcting the frequency characteristics Fhls and Fhlo can be 10 Hz to 20 kHz. In other words, the correction unit 225 does not correct the amplitude value in the band from the lowest frequency (for example, 1 Hz) to less than 10 Hz and in the band from 20 kHz to the highest frequency. Therefore, the amplitude values of the frequency characteristics Fhls and Fhlo are used as they are outside the correction band. The correction band may be changed according to the reproduction band of the headphone 43 for out-of-head localization reproduction, that is, the headphone 43 in FIG.

Filter generator 230 generates a correction filter based on the correction characteristic. Specifically, the filter generating section 230 includes an inverse transforming section 232 and an adjusting section 231 . The inverse transform unit 232 inverse transforms the correction characteristic to generate a time-domain correction signal. The inverse transform unit 232 calculates a correction signal in the time domain from the correction characteristic and the phase characteristic by inverse discrete Fourier transform or inverse discrete cosine transform. The inverse transform unit 232 performs IFFT (inverse fast Fourier transform) on the correction characteristic and the phase characteristic to generate a correction signal in the time domain. A correction signal hls2 obtained from the correction characteristic NewFhls is assumed. A correction signal hlo2 obtained from the correction characteristic NewFhlo is assumed. The correction signals hls2 and hlo2 are filters having the same filter length as the collected sound signal after clipping.

As the phase characteristic, the phase characteristic calculated by the frequency characteristic acquisition unit 221 can be used as it is. That is, the inverse transform unit 232 generates the correction signal hls2 by performing inverse Fourier transform on the phase characteristic corresponding to the frequency characteristic Fhls and the correction characteristic NewFhls. The inverse transform unit 232 performs inverse Fourier transform on the phase characteristic corresponding to the frequency characteristic Fhlo and the correction characteristic NewFhlo to generate the correction signal hlo2.

The segmental power acquisition unit 215 acquires segmental powers of the correction signal hls2 and the correction signal hlo2. As mentioned above, the segmental power can be the sum of the squares of the amplitude values of the signal in the time domain. Let hls2P be the segmental power of the correction signal hls2, and hlo2 be the segmental power of the correction signal hlo2.

The adjuster 231 adjusts the powers of the correction signals hls2 and hlo2 so as to maintain the left and right power ratio (energy ratio). The adjuster 231 amplifies the correction signal so that the power ratios before and after the correction match. For example, the adjuster 231 multiplies the amplitude value of the correction signal by a predetermined number. The predetermined number for the correction signal hls2 is (hlsP/hlsP2), and the predetermined number for the correction signal hlo2 is (hloP/hloP2).

The correction signals hls2 and hlo2 after adjusting the power ratio are used as correction filters hls3 and hlo3. The product of the amplitude value of the correction signal hls2 and a predetermined number (hlsP/hlsP2) is the amplitude value of the correction filter hls3. The product of the amplitude value of the correction signal hlo2 and a predetermined number (hloP/hloP2) is the amplitude value of the correction filter hlo3. Therefore, the segmental power of the correction filter hls3 is the same as the segmental power of the collected sound signal hls. The segmental power of the correction filter hlo3 is the same as the segmental power of the collected sound signal hlo.

By doing so, an appropriate correction filter can be generated. That is, the processing device 201 can generate a correction filter according to the playback device. The correction filters hls3 and hlo3 are set as spatial acoustic filters in the convolution calculation units 11 and 12 shown in FIG. As a result, the out-of-head localization processing apparatus 100 can perform reproduction with a high out-of-head localization effect.

Specifically, the correction characteristics are generated so as to fall within the level range X according to the playback device. Therefore, measurement and out-of-head localization processing can be performed in a state suitable for playback equipment. Therefore, a filter suitable for out-of-head localization processing can be generated.

Furthermore, in the above-described embodiment, the adjusting section 231 adjusts the left-right balance. It is possible to realize out-of-head localization reproduction with a good left/right balance. Of course, the adjustment of the power balance by the adjusting section 231 can be omitted. For example, when the processing device 201 processes a single collected sound signal hls, the processing of the adjustment unit 231 is omitted. In this case, the correction signal hls2 is directly set in the convolution calculator 11 as a correction filter.

The processing device 201 can similarly process the collected sound signals indicating the spatial sound transfer characteristics Hro and Hrs. In this case, the filter generating section 230 adjusts the correction signal so that the segmental power ratio of the collected sound signals indicating the spatial sound transfer characteristics Hro and Hrs is maintained before and after the correction. Furthermore, the processing device 201 can similarly process the ear canal transfer characteristics of both ears. In the processing device 201, the filter generator 230 adjusts the correction signal so that the segmental power ratio between the left ear ear canal transfer characteristic ECTFL and the right ear ear canal transfer characteristic ECTFR is maintained before and after the correction.

Next, a filter generation method according to this embodiment will be described with reference to FIG. FIG. 5 is a flow chart showing the filter generation method.

First, the measuring device 200 measures transfer characteristics using impulse sound or the like (S101). That is, the measurement signal generator 211 outputs a measurement signal such as an impulse sound from the left speaker 5L. The collected sound signal acquisition unit 212 acquires the collected sound signal from the microphone unit 2 (S102). The collected sound signal acquisition unit 212 cuts out the collected sound signal from the left microphone 2L and the collected sound signal from the right microphone 2R with a predetermined filter length. As a result, picked-up sound signals hls and hlo are obtained.

The segmental power acquisition unit 215 calculates segmental powers of the collected sound signals hls and hlo (S103). The frequency characteristic acquisition unit 221 Fourier-transforms the collected sound signal (S104). As a result, frequency characteristics Fhls and Fhlo are obtained. The frequency characteristic is a frequency amplitude characteristic (amplitude spectrum), but may be a frequency power characteristic (power spectrum).

The level calculator 223 calculates the reference level (S105). As described above, the reference level is the average value of the amplitude values of the two frequency characteristics Fhls and Fhlo. Further, the level calculator 223 calculates the maximum level and minimum level of the frequency characteristics Fhls and Fhlo. The reference level, maximum level, and minimum level may be calculated from the amplitude values of all bands or from the amplitude values of some bands.

Also, the level range for compression is set by the level range setting unit 224 (S106). The level range is set according to the model, performance, etc. of the playback device. For example, a user or filter generation staff may enter the level range X. Then, the correction unit 225 compresses and corrects the frequency characteristics Fhls and Fhlo so that the amplitude values of the frequency characteristics Fhls and Fhlo fall within the level range X including the reference level (S107). As a result, correction characteristics NewFhls and NewFhlo are obtained. The amplitude values of the correction characteristics NewFhls and NewFhlo are included in the level range X.

Next, the inverse transform unit 232 inverse Fourier transforms the correction characteristics (S108). In the inverse Fourier transform, the frequency-amplitude characteristic is the correction characteristic, and the frequency-phase characteristic is the frequency-phase characteristic calculated by the Fourier transform in S104. As a result, a correction signal hls2 and a correction signal hlo2 in the time domain are obtained.

The amplitude levels of the correction signal hls2 and the correction signal hlo2 are adjusted so that the adjustment unit 231 maintains the segmental power ratio of the collected sound signals hls and hlo (S109). Specifically, the adjustment unit 231 multiplies the correction signal hls2 and the correction signal hlo2 by a predetermined number according to the segmental power ratio. As a result, a correction filter hls3 and a correction filter hlo3 are obtained. By adjusting the power ratio by the adjusting unit 231, a filter with good left-right balance can be generated.

(Correction processing example 1)
Next, an example of the correction step of step S107 will be described with reference to FIG. FIG. 6 is a flow chart showing a processing example 1 of correction processing by the correction unit 225 .

First, the correction unit 225 determines whether or not the level difference of the frequency-amplitude characteristics is equal to or greater than the level range X (S201). The level difference is the level difference (maxL-minL) between the maximum value (maximum level maxL) and the minimum value (minimum level minL). The maximum level and minimum level may be the maximum and minimum values of the frequency-amplitude characteristic in the entire band, or may be the maximum and minimum values of a partial band.

If the level difference is smaller than the level range X (NO in S201), the correction unit 225 terminates the process without correction. If the difference is greater than the level range X (NO in S201), the correction section 225 compresses the level (amplitude value) of each frequency toward the reference level (S202). As a result, the frequency characteristic is corrected so that the level at each frequency falls within the level range X. FIG.

7 is a graph showing frequency-amplitude characteristics before and after correction in Processing Example 1. FIG. That is, FIG. 7 shows amplitude spectra of the frequency characteristic Fhls before correction and the corrected characteristic NewFhls. As shown in FIG. 7, the corrected frequency-amplitude characteristic falls within the level range X centered on the reference level A. FIG. In FIG. 7, the reference level A=-9.4 dB and the level range X=20 dB. Furthermore, in FIG. 7, 10 Hz to 20 kHz are set as the correction band.

(Correction processing example 2)
Next, another example of the correction step of step S107 will be described with reference to FIG. FIG. 8 is a flowchart showing a processing example 2 of the correction processing by the correction unit 225. FIG. In processing example 2, the correction unit 225 corrects only levels (amplitude values) greater than the reference level.

First, the correction unit 225 determines whether or not the level difference of the frequency-amplitude characteristics is equal to or greater than the level range X (S301). The level difference is the difference value (maxL-minL) between the maximum value (maximum level maxL) and the minimum value (minimum level minL). The maximum level and minimum level may be the maximum and minimum values of the frequency-amplitude characteristic in the entire band, or may be the maximum and minimum values of a partial band.

If the level difference is smaller than the level range X (NO in S301), the correction unit 225 terminates the process without correction. If the difference is greater than the level range X (YES in S301), the correction unit 225 compresses only the levels (amplitude values) of each frequency greater than the reference level toward the reference level (S302). The correction unit 225 lowers the level higher than the reference level.

Note that, in Processing Example 2, the correction unit 225 does not perform correction for levels smaller than the reference level. Therefore, at frequencies lower than the reference level, the amplitude values match before and after the correction.

Further, in the processing example 2, the correction unit 225 corrects only levels higher than the reference level, but may correct only levels lower than the reference level. In other words, in Processing Example 2, the correction unit 225 corrects only one of the level higher than the reference level and the level lower than the reference level. The correction section 225 may correct the frequency characteristics only at a level equal to or higher than the reference level or at a level equal to or lower than the reference level.

FIG. 9 is a graph showing frequency-amplitude characteristics before and after correction in Processing Example 2. FIG. In FIG. 9, the reference level A=-9.4 dB and the level range X=20 dB. Furthermore, in FIG. 9, 10 Hz to 20 kHz are set as the correction band. As shown in FIG. 9, amplitude values higher than the reference level A have frequency-amplitude characteristics after correction within the level range X. FIG. In this case, at levels lower than the reference level A, the level range X may not be satisfied. In other words, in Processing Example 2, the frequency-amplitude characteristic falls within the level range of the min level or more and (A+(X/2)) or less.

(Correction processing example 3)
In Processing Example 3, the frequency axis of the frequency-amplitude characteristic is scaled logarithmically. The reason for converting the frequency axis to the logarithmic scale will be explained. Generally, it is said that the human sensory quantity is converted into a logarithm. Therefore, it is important to consider the frequency of the sound we hear on a logarithmic axis. By converting the scale, the data are evenly spaced in the sensory quantity, so that the data can be handled equally in all frequency bands. As a result, mathematical operations, division and weighting of frequency bands become easier, and stable results can be obtained. Note that the frequency characteristic acquisition unit 221 is not limited to the logarithmic scale, and may convert the envelope data to a scale close to human hearing (referred to as an auditory scale). As the auditory scale, the logarithmic scale, the mel scale, the Bark scale, the ERB (Equivalent Rectangular Bandwidth) scale, or the like may be used for axis conversion.

The frequency characteristic acquisition unit 221 scale-converts the spectrum data on an auditory scale by data interpolation. For example, the frequency characteristic acquisition unit 221 interpolates data in the low frequency band with coarse data intervals in the auditory scale, thereby increasing the density of the data in the low frequency band. Equally-spaced data on an auditory scale is dense in the low-frequency band and rough in the high-frequency band on a linear scale. By doing so, the frequency characteristic acquisition unit 221 can generate axis transformation data at equal intervals on an auditory scale. Of course, the axis-transformed data does not have to be perfectly evenly spaced data on the auditory scale. By doing so, the correction unit 225 and the like perform processing on the logarithmic scale frequency-amplitude characteristic. Also, in order to match the frequency phase characteristic and the number of samples, the frequency axis may be returned to a linear scale before the inverse transform.

(Correction processing example 4)
In processing example 4, the correction unit 225 corrects the amplitude value only at frequencies around the peak exceeding the upper limit value of the level range X, instead of correcting the entire correction band. Processing example 4 will be described with reference to FIG. 10 . FIG. 10 is a flowchart showing a fourth processing example.

First, the correction unit 225 determines whether or not the level difference of the frequency-amplitude characteristics is equal to or greater than the level range X (S401). The level difference is the difference value (maxL-minL) between the maximum value (maximum level maxL) and the minimum value (minimum level minL). The maximum level and minimum level may be the maximum and minimum values of the frequency-amplitude characteristic in the entire band, or may be the maximum and minimum values of a partial band.

If the level difference is smaller than the level range X (NO in S401), the correction unit 225 terminates the process without correction. If the difference is greater than the level range X (NO in S201), the correction unit 225 compresses the amplitude value toward the reference level around the peak frequency that exceeds the upper limit value (A+X/2) of the range. (S402).

For example, the correction unit 225 obtains crossover frequencies that cross the upper limit before and after the peak frequency. The correction unit 225 calculates a first crossover frequency lower than the peak frequency and a second crossover frequency higher than the peak frequency. The correction unit 225 compresses the amplitude value toward the reference level in the frequency band defined by the first crossover frequency and the second crossover frequency.

Specifically, the correction unit 225 obtains a first crossover frequency that crosses the upper limit value of the range on the lower frequency side than the peak frequency. The correction unit 225 obtains a second crossover frequency that crosses the upper limit value of the range on the higher frequency side than the peak frequency. The corrector 225 corrects the amplitude value in the frequency band from the first crossover frequency to the second crossover frequency. By doing so, it is possible to correct the amplitude value exceeding the upper limit value of the range around the peak.

FIG. 11 is a graph showing three frequency bands (a)-(c) defined by crossover frequencies. The frequency band (a) is the frequency band containing the first peak P1. That is, the frequency band (a) is defined by crossover frequencies before and after the first peak P1. The frequency band (b) is the frequency band containing the second peak P2. The frequency band (c) is the frequency band containing the third peak P3. Also, as shown in FIG. 11, one frequency band may include multiple peaks that are close together.

In this way, in processing example 4, only amplitude values exceeding only the upper limit value of the range are compressed toward the reference level. Further, the correction section 225 may correct the amplitude value at the frequency around the dip below the lower limit of the level range X (A-(X/2)). Also in this case, the correction unit 225 obtains crossover frequencies that intersect the lower limit value before and after the dip below the lower limit value. Correction section 225 may compress the amplitude value in the frequency band defined by the two crossing frequencies. Of course, the correction section 225 may compress the amplitude values in both the frequency band including the peak and the frequency band including the dip. Alternatively, the correction unit 225 may compress the amplitude value only in the frequency band containing the peak, or may compress the amplitude value only in the frequency band containing the dip.

(Correction processing example 5)
In processing example 5, the correction unit 225 performs correction using a different method. Specifically, smoothing processing such as moving average is used to correct the level of the amplitude value. The frequency characteristics (spectrum data) are smoothed using techniques such as moving average, Savitzky-Golay filter, smoothing spline, cepstrum transform, and cepstrum envelope. The correction unit 225 corrects the frequency characteristic so that it falls within the level range X by performing smoothing processing on the frequency characteristic.

(Correction processing example 6)
In processing example 6, the collected sound signal is processed for the ear canal transfer characteristics. That is, the measurement device 300 shown in FIG. 3 is performing the measurement. Specifically, in the processing device 201 shown in FIG. 4, the measurement signal generator 211 outputs the measurement signal to the headphone 43 instead of the speaker 5L. In this case, the left and right microphones 2L and 2R pick up sound pickup signals indicating the ear canal transfer characteristics of the left and right ears. Get the frequency-amplitude characteristics. A reference level, a maximum level and a minimum level are obtained from the two frequency amplitude characteristics. Contents other than the above points are the same as those of the above-described embodiment and processing example, and therefore description thereof is omitted.

(Correction processing example 7)
In processing example 7, multi-channel speakers such as 5.1ch and 7.1ch are used. Then, the adjustment unit 231 performs adjustment so that the power ratio of the collected sound signal is maintained for each channel.

In 5.1ch multi-channel, left and right front speakers, left and right rear speakers, a center speaker, and a subwoofer are used. In this case, the adjustment section 231 adjusts the correction signal so that the power ratio between the front speakers and the rear speakers is maintained. Specifically, the adjustment unit 231 multiplies each correction signal by a coefficient that makes the segmental power ratio before and after correction the same.

Specifically, the measurement apparatus 200 sequentially performs measurements using speakers of different channels. For example, the measurement signal generator 211 generates measurement signals and sequentially outputs them to the speakers of each channel. The collected sound signal acquisition unit 212 acquires an acquired signal by sequentially collecting the measurement signal from the speaker of each channel. The frequency characteristic acquisition unit 221 acquires a plurality of frequency characteristics based on the collected sound signals obtained by collecting measurement signals output from speakers of different channels.

The segmental power acquisition unit 215 calculates the left and right segmental powers of the collected sound signal for each channel. The adjuster 231 adjusts the level of the correction signal so as to maintain the power ratio. By doing so, a filter with good balance between channels can be generated. Note that the level range X may be different for each channel, or may be the same between channels.

It should be noted that the process of maintaining the power ratio between channels is not limited to multi-channel such as 5.1ch, and can also be applied to the 2ch measurement apparatus shown in FIG. For example, left and right speaker measurements may be taken and adjusted to maintain the power ratio.

The above processing examples 1 to 7 can be combined as appropriate. For example, when correcting the amplitude value around the peak frequency or the dip frequency as in Processing Example 4, the correction unit 225 performs the frequency axis conversion processing in Processing Example 3 and the smoothing processing in Processing Example 5. may be used.

As described above, according to the present embodiment, the frequency characteristic is corrected so as to fall within the predetermined level range X including the reference level. Therefore, it is possible to reproduce a filter capable of obtaining an appropriate out-of-head localization effect even with various reproduction equipment, equipment, and measurement environments. In other words, it is possible to automatically correct a filter that does not clip the signal subjected to out-of-head localization processing. Out-of-head localization listening can be performed according to the user's preferences, speakers, headphones, and the measurement environment. Furthermore, automatic correction according to the playback equipment becomes possible.

Embodiment 2.
A device and method according to Embodiment 2 will be described with reference to FIG. FIG. 12 is a block diagram showing the configuration of the processing device 201. As shown in FIG. One of the technical features of the second embodiment is the process of setting the level range X. FIG. Therefore, the processing device 201 shown in FIG. 12 has a determination unit 242 added to the configuration of FIG. Configurations and processes other than the determination unit 242 are the same as those in the first embodiment, and thus description thereof will be omitted as appropriate.

A determination unit 242 determines the performance of the playback device. For example, the determination unit 242 evaluates the performance of the amplifier of the playback device. The level range setting section 224 sets the level range X according to the determination result of the determination section 242 . The correction unit 225 corrects the frequency characteristic based on the level range X to calculate the corrected characteristic. Filter generator 230 generates a correction filter based on the correction characteristic.

For example, the determination unit 242 can make determinations based on the frequency characteristics acquired by the frequency characteristics acquisition unit 221 . The determination section 242 detects the level difference (maxL-minL) between the maximum level (maxL) and the minimum level (minL) of the frequency-amplitude characteristic. The determination unit 242 acquires the output level (output sound pressure level) and S/N ratio of the playback device based on the level difference. Then, the determination unit 242 determines the performance based on the output level or S/N ratio. The determination section 242 may determine the level range X according to the level difference between the maximum level and the minimum level of the frequency-amplitude characteristic.

For example, in the case of a playback device with a large level difference, the level range X should be about 80% of the level difference. The determination unit 242 sets the variable as 0.8. In the case of a playback device with a small level difference, the level range X is set to about 40% of the level difference. The level range setting unit 224 sets the level range X by multiplying the level difference by a variable according to the determination result.

Also, the processing device 201 can set the level range X without using variables. For example, the determination section 242 calculates the level difference (maxL-minL) in some determination bands. The decision band can be, for example, 100 Hz to 8 kHz. That is, the determination section 242 obtains the maximum level (maxL) and minimum level (minL) in the range of 100 Hz to 8 kHz. Then, the determination unit 242 makes a determination based on the level difference (maxL-minL). Alternatively, the determination section 242 may have a conversion formula or a conversion table for converting the level difference into the level range X. FIG.

In this manner, the determination unit 242 performs determination based on the frequency characteristics of the collected sound signal obtained by measurement using the playback device. The determination unit 242 makes a determination based on the level difference between the maximum level and the minimum level of the frequency characteristics.

Also, the determination unit 242 may acquire playback device information about the playback device and determine the performance based on the playback device information. Then, the level range setting section 224 sets the level range X according to the performance of the playback device. For example, if the amplifier of the playback device has high performance, the level range setting section 224 sets X=40 dB. If the amplifier has low performance, the level range setting section 224 sets X=20 dB. Of course, the determination by the determination unit 242 is not limited to two stages of high performance and low performance, and may be three stages or more.

Also, the determination unit 242 may have a table showing performance for each model number of the playback device. The determination unit 242 acquires playback device information indicating the model number of the playback device. The determination unit 242 determines the performance according to the model number of the playback device. The playback device information regarding the playback device may be automatically acquired or input by the user, for example. For example, in the case of a playback device with a BlueTooth connection, the determination unit 242 can automatically acquire information about the playback device.

For example, the measuring device 200 or the measuring device 300 performs measurements in advance for each playback device to acquire the frequency characteristics. Then, as described above, the determination unit 242 determines the performance according to the level difference of the frequency characteristics, and stores the determination result in the table. Then, the determination unit 242 can refer to the table and make a determination.

The reproducing device may be the speakers 5L and 5R and their amplifiers shown in FIG. 2, or the headphones 43 shown in FIG. That is, the playback device may be the playback device used during measurement. Alternatively, the headphones 43 in the out-of-head localization processing apparatus shown in FIG. 1 may be used. In other words, the playback device may be the headphones 43 or earphones used for out-of-head localization listening. Any one or more of the above processing examples 1 to 7 can also be used in the second embodiment.

Thus, according to the present embodiment, it is possible to automatically set the level range X according to the performance of the playback device. Then, the correction unit 225 performs correction based on the level range X. FIG. Therefore, it is possible to reproduce a filter capable of obtaining an appropriate out-of-head localization effect even with various reproduction equipment, equipment, and measurement environments. In other words, it is possible to automatically correct a filter that does not clip the signal subjected to out-of-head localization processing. Out-of-head localization listening can be performed according to the user's preferences, speakers, headphones, and the measurement environment. Furthermore, automatic correction according to the playback equipment becomes possible.

A part or all of the above processes may be executed by a computer program. The programs described above include instructions (or software code) that, when read into a computer, cause the computer to perform one or more of the functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or tangible storage medium. By way of example, and not limitation, computer readable media or tangible storage media may include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drives (SSD) or other memory technology, CDs -ROM, digital versatile disc (DVD), Blu-ray disc or other optical disc storage, magnetic cassette, magnetic tape, magnetic disc storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or communication medium. By way of example, and not limitation, transitory computer readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

The invention made by the present inventor has been specifically described above based on the embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

U User 1 Subject 2 Microphone unit 2L Left microphone 2R Right microphone 5 Stereo speaker 5L Left speaker 5R Right speaker 10 Out-of-head localization processor 11 Convolution calculator 12 Convolution calculator 21 Convolution calculator 22 Convolution calculator 24 Adder 25 Adder 41 filter section 42 filter section 43 headphone 200 measurement device 201 processing device 211 measurement signal generation section 212 collected sound signal acquisition section 215 segmental power acquisition section 221 frequency characteristic acquisition section 223 level calculation section 224 level range setting section 225 correction section 230 filter generation unit 231 adjustment unit 232 inverse transform unit 242 determination unit

Claims (5)

a frequency characteristic acquisition unit that acquires frequency characteristics based on the collected sound signal;
a level calculator that calculates a reference level in the frequency characteristic;
a correction unit that calculates a correction characteristic by correcting the frequency characteristic so as to fall within a predetermined level range including the reference level;
and a filter generation unit that generates a correction filter based on the correction characteristic. The frequency characteristic acquisition unit,
Acquiring a first frequency characteristic based on a first sound pickup signal picked up by the left microphone worn on the left ear of the user;
Acquiring a second frequency characteristic based on a second sound pickup signal picked up by a right microphone worn on the right ear of the user;
The level calculation unit calculates a common level for the first frequency characteristic and the second frequency characteristic,
The correction unit
calculating a first correction characteristic obtained by correcting the first frequency characteristic and a second correction characteristic obtained by correcting the second frequency characteristic;
The filter generation unit
generating a first correction signal and a second correction signal in the time domain by inversely transforming the first correction characteristic and the second correction characteristic, respectively;
2. The filter generation device according to claim 1, wherein the levels of said first correction signal and said second correction signal are adjusted so as to maintain a left and right power ratio before and after correction. The frequency characteristic acquisition unit acquires a plurality of frequency characteristics based on a sound pickup signal obtained by sequentially collecting measurement signals output from speakers of different channels,
3. The filter generation device according to claim 2, wherein the level of the correction signal is adjusted so as to maintain the power ratio of the collected sound signal for each channel. 4. The filter generation device according to any one of claims 1 to 3, wherein the correction unit corrects the frequency characteristic only at levels equal to or higher than the reference level or at levels equal to or lower than the reference level. a step of obtaining frequency characteristics based on the collected sound signal;
calculating a reference level in the frequency characteristic; calculating a correction characteristic by correcting the frequency characteristic so as to fall within a predetermined level range including the reference level;
and generating a filter based on the correction characteristic.

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