JP6841002B2 - Acoustic characteristic measurement method, acoustic characteristic measurement device and acoustic characteristic measurement program - Google Patents

Description

The present invention relates to an acoustic characteristic measuring method, an acoustic characteristic measuring device, and an acoustic characteristic measuring program.

A certain space such as a closed room (listening room) or a partially open booth is used as an audio space for listening to the sound of music, movies, etc., for example. In such an audio space, the sound waves emitted by the speaker are reflected by the wall or ceiling and overlap or cancel each other, so that the sound pressure level of a specific frequency is increased or decreased. A sound wave having a wavelength at which the sound pressure level increases or decreases due to the overlapping of reflected waves is called a standing wave and has a frequency peculiar to the audio space.

The frequency of such a standing wave is measured and corrected so that a flat frequency characteristic can be obtained. For example, by arranging a sound absorbing material having a high sound absorbing coefficient for a specific frequency in the audio space, it is possible to reduce a standing wave having a peak sound pressure.

In addition, by providing a filter that selectively attenuates the falling part of the signal at the peak position or the dip position (standing wave frequency) of the acoustic signals input to the speaker, the sound that corrects the reverberation that is a problem in hearing is corrected. A treatment method has also been proposed (see Patent No. 5290949).

In the acoustic processing method described in the above-mentioned publication, a test signal is emitted from a speaker, and an impulse response waveform obtained by collecting sound with a microphone arranged at a listening point is fixed from the frequency characteristics obtained by Fourier transform or Adamal transform. The peak and dip frequencies due to the wave are specified.

However, the frequency specified by the method as described in the above publication may be different from the frequency of the standing wave that gives the listener a sense of discomfort.

Japanese Patent No. 5290949

In view of the above inconvenience, it is an object of the present invention to provide an acoustic characteristic measuring method, an acoustic characteristic measuring device, and an acoustic characteristic measuring program capable of relatively accurately specifying the frequency of a standing wave that gives a listener a sense of discomfort. And.

The invention made to solve the above problems is a method of measuring the acoustic characteristics of an audio space, which includes a step of acquiring an impulse response waveform of a sound wave using an audio reproduction speaker as an input source at a listening point, and the impulse. The method for measuring acoustic characteristics is characterized by including a step of analyzing a response waveform and determining a frequency at which the sound pressure level drops slowly or quickly as a standing wave frequency. The "slow frequency or fast frequency" means a frequency or frequency that is slower than other frequencies.

The determination step identifies a frequency band having a relatively long reverberation time or a frequency band having a relatively short reverberation time from the step of deriving the sound pressure level change for each frequency band from the impulse response waveform and the sound pressure level change for each frequency band. It is preferable to have a step and a step of determining the peak or dip of the frequency characteristic in the frequency band having a relatively long reverberation time or the short frequency band as the standing wave frequency as the standing wave frequency.

In the determination step, the impulse response waveform of the frequency band having a relatively long reverberation time or the frequency band having a relatively short reverberation time may be Fourier transformed.

Weighting may be performed according to the frequency in the determination step.

It is preferable that the acquisition step is performed separately for the left and right sides of the audio reproduction speaker, and the standing wave frequency is determined separately for the left and right sides in the determination step.

Another invention made to solve the above problems is a device for measuring the acoustic characteristics of an audio space, a sound generation mechanism for outputting an impulse input wave using an audio reproduction speaker, and a listening point. It is provided with a recording mechanism for recording the impulse response waveform obtained by the impulse input wave and a calculation mechanism for analyzing the impulse response waveform and determining a frequency with a slow or fast sound pressure level drop as a standing wave frequency. It is an acoustic characteristic measuring device characterized by.

Yet another invention made to solve the above problems is a program for measuring the acoustic characteristics of the audio space using a programmable device having an audio input unit and an audio output unit, from the audio output unit. An input control element that outputs an impulse input wave, a recording control element that records an impulse response waveform input to the audio input unit when the impulse input wave is output, and a frequency at which the sound pressure level drops slowly by analyzing the impulse response waveform. Alternatively, it is an acoustic characteristic measurement program characterized by including an arithmetic element for determining a fast frequency as a standing wave frequency.

The acoustic characteristic measuring method, the acoustic characteristic measuring apparatus, and the acoustic characteristic measuring program of the present invention analyze the impulse response waveform and determine that the frequency at which the sound pressure level drops slowly or early is the standing wave frequency, which makes the listener feel uncomfortable. The frequency of the standing wave that gives the above can be specified relatively accurately.

It is a schematic diagram which shows the structure of the acoustic characteristic measuring apparatus of one Embodiment of this invention. It is a flowchart which shows the procedure of the acoustic characteristic measurement method using the acoustic characteristic measurement apparatus of FIG. This is an example of the impulse response waveform obtained in the acquisition step of FIG. This is an example of a pulse glide figure derived in the determination step of FIG. It is a flowchart which shows the preferable detailed procedure of the determination process of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Acoustic characteristic measuring device]
The acoustic characteristic measuring device according to the embodiment of the present invention shown in FIG. 1 is an apparatus for measuring the acoustic characteristics of an audio space. More specifically, the acoustic characteristic measuring device is a device that measures the frequency of a standing wave peculiar to the audio space.

The acoustic characteristic measuring device includes a sound generation mechanism 1 that outputs an impulse input wave using an audio reproduction speaker (speaker SL on the left side and a speaker SR on the right side), and a listening point (for example, on a sofa) where the listener is normally located. ), The recording mechanism 2 that records the impulse response waveform obtained by the impulse input wave, and the arithmetic mechanism 3 that analyzes the impulse response waveform and determines a frequency with a slow or fast sound pressure level drop as a standing wave frequency. To be equipped with.

In the acoustic characteristic measuring device, the sound generation mechanism 1, the recording mechanism 2, and the arithmetic mechanism 3 are functionally distinguished, and 2 or all the mechanisms may be realized by the same computer or the like.

Further, it is preferable that the acoustic characteristic measuring device further includes an interface 4 capable of setting the sound generation mechanism 1, the recording mechanism 2, and the calculation mechanism 3.

<Sound generation mechanism>
The sound generation mechanism 1 may be any as long as it outputs an impulse input wave from the speakers SL and SR installed in the audio space. For example, an audio system that records impulse input wave data and is connected to the speakers SL and SR. It can be composed of a recording medium such as a CD that can be reproduced by the computer, an audio signal output device such as a portable player that is wiredly connected to an external input terminal of an audio system or wirelessly connected to a wireless module. As the portable player, for example, a programmable device such as a smartphone, a mobile computer, or a personal computer in which an audio reproduction program is installed may be used.

<Recording mechanism>
The recording mechanism 2 is a recording system having a microphone 5 arranged at a position where a listener actually listens to sound, and a recording means 6 for recording an electric signal output by the microphone 5 as electronic data. As the recording mechanism 2, for example, a programmable device having a voice input / output function such as a smartphone, a mobile computer, or a personal computer may be used with a voice recording program installed.

<Calculation mechanism>
The calculation mechanism 3 derives the frequency distribution of the sound pressure level from the impulse response waveform recorded by the recording mechanism 2, identifies a frequency in which the sound pressure level drops slower or faster than other frequencies, and determines this frequency. The frequency of the current wave. The calculation method for specifying the frequency of the standing wave will be described in detail later in relation to the acoustic characteristic measurement method.

<Interface>
The interface 4 has, for example, a display means 7 for presenting information to an operator (acoustic characteristic measurer) such as a liquid crystal panel, and an input means 8 for an operator such as a keyboard, a switch, or a touch sensor to make settings. It is preferable to do so. As the interface 4, for example, one in which a display means 7 such as a touch panel and an input means 8 are integrated is particularly preferably used.

[Acoustic characteristic measurement method]
The acoustic characteristic measuring method according to another embodiment of the present invention shown in FIG. 2 is a method for measuring the acoustic characteristic of the audio space, and can be performed by using the acoustic characteristic measuring apparatus of FIG. Therefore, in the description of the present embodiment, the reference numerals of FIG. 1 are used for easy understanding, but the acoustic characteristic measuring method is not limited to the method of using the acoustic characteristic measuring apparatus of FIG.

The acoustic characteristic measurement method includes a step <step S1: acquisition step> of acquiring an impulse response waveform of a sound wave using audio reproduction speakers SL and SR as input sources at a listening point, and an analysis of the impulse response waveform to sound pressure. A step <step S2: determination step> of determining a frequency with a slow or fast level drop as a standing wave frequency is provided.

<Acquisition process>
In the acquisition step of step S1, the impulse input wave is output by the speakers SL and SR, and the sound wave reflected directly from the speakers SL and SR or by the surrounding wall or the like and incident on the microphone 5 arranged at the listening point is recorded by the recording means 6. Record. It is preferable that this acquisition step is performed separately for the left speaker SL and the right speaker SR, that is, two impulse response waveforms are acquired.

The impulse input wave may be an impulse waveform signal, but a known waveform signal from which an impulse response waveform can be obtained, for example, a TSP (Time Stretched Pulse) signal, an M-sequence (Maximum Lens Sequence) signal, or the like can be used. By using a TSP signal or an M-sequence signal, an impulse response waveform having a large S / N ratio can be obtained. When a TSP signal or an M-sequence signal is used, an impulse response waveform as illustrated in FIG. 3 can be obtained by performing known signal processing on the waveform obtained by the microphone 5 according to the type of the signal.

<Judgment process>
In the determination step of step S2, the impulse response waveform is analyzed to confirm the change in sound pressure level for each frequency. Specifically, by deriving, for example, a pulse glide, a cumulative phase spectrum, or the like as illustrated in FIG. 4 from the impulse response waveform, changes in the sound pressure level for each frequency can be confirmed relatively easily. In the pulse glide figure illustrated in FIG. 4, the vertical axis represents frequency, the horizontal axis represents time, and the sound pressure level is represented by a color (in FIG. 4, the larger the color, the darker the color).

As a method of identifying a frequency in which the sound pressure level drops slowly or early using such data, a frequency in which the sound pressure level at the judgment reference time is equal to or higher than the peak threshold value or lower than the dip threshold value is specified, and this frequency is fixed. It can be determined to be the wave frequency. More specifically, the standing wave frequency can be, for example, the median of a frequency range in which the sound pressure level is continuously above or below the peak threshold or below the dip threshold.

The determination reference time, peak threshold value and dip threshold value are such that the frequency range in which the sound pressure level is continuously equal to or higher than the peak threshold value or lower than the peak threshold value is equal to or lower than a certain frequency width, and the sound pressure level is equal to or higher than the peak threshold value or lower than the dip threshold value. The number of frequency bands to be used may be adjusted automatically or by the operator via the interface 4 so as to be less than or equal to a certain number.

Further, it is preferable that the standing wave frequency is determined separately for the impulse response waveform with the left speaker SL as the input and the impulse response waveform with the right speaker SR as the input. As a result, it is possible to appropriately improve the acoustic characteristics of the audio space by adding the left-right asymmetry of the audio space. Examples of the method for improving the acoustic characteristics of the audio space include a method of arranging the sound absorbing member in the audio space.

In this determination step, weighting may be performed according to the frequency. That is, a value obtained by multiplying the sound pressure level by a coefficient set in advance according to the frequency may be compared with the peak threshold value or higher or the dip threshold value. As a result, the change in the sound pressure level of the frequency that is easily heard by human hearing can be reflected more greatly, so that the frequency of the standing wave that gives a sense of discomfort to the listener can be preferentially specified.

Further, in the determination step, the frequency at which the sound pressure level drops slowly or quickly is specified, as shown in FIG. 5, a step of deriving the sound pressure level change for each frequency band from the impulse response waveform (S21: deriving step). A step of specifying a frequency band having a relatively long reverberation time or a frequency band having a relatively short reverberation time from the change in sound pressure level for each frequency band (step S22: specifying step) and the reverberation time relatively as a standing wave frequency It is preferable to adopt a method having a step (step S23: determination step) of determining the peak or dip of the frequency characteristic in the long frequency band or the short frequency band as the standing wave frequency.

In this way, by using the change in the average sound pressure level in the frequency band as an index, it is possible to identify the frequency band including the peak or dip of the acoustic characteristic in which the unnaturalness is more easily recognized by human hearing. Conversely, by adopting the method of FIG. 5, it is possible to exclude peaks or dips that cause slight sound distortion that is difficult for human hearing to distinguish due to the extremely small frequency width of the peaks or dips.

(Derivation process)
In the derivation step of step S21, the sound pressure level change is derived for each fixed frequency band such as an octave band and a 1/3 octave band. As a specific example, by averaging the sound pressure levels of each frequency band in the pulse glide of FIG. 4 over time, a change in the average sound pressure level of each frequency band is obtained.

(Specific process)
In the specific step of step S22, an index representing the reverberation time is derived from the change in the average sound pressure level of each frequency band obtained in the derivation step. In addition to the reverberation time, examples of the index representing the reverberation time include, for example, the time when the sound pressure level is equal to or higher than the threshold value, the sound absorption coefficient, and the like. Then, by comparing the index of the reverberation time of each frequency band, one or a plurality of frequency bands having a relatively long reverberation time, or one or a plurality of frequency bands having a relatively short reverberation time are specified.

The derivation step and the specific step can be performed using data obtained by superimposing a sound pressure level change with the left speaker SL as an input and a sound pressure level change with the right speaker SR as an input. In this way, the amount of calculation can be reduced by collectively narrowing down the frequency band by superimposing the left and right data.

(Decision process)
In the determination step of step S23, the frequency at which the frequency characteristic of the sound pressure level peaks or dips within the frequency band or the frequency band having a relatively long reverberation time specified in the specific step is determined as the standing wave frequency. To do.

It is preferable that this derivation step is performed separately for the sound pressure level change with the left speaker SL as an input and the sound pressure level change with the right speaker SR as an input. As a result, it is possible to appropriately improve the acoustic characteristics of the audio space by adding the left-right asymmetry of the audio space.

Further, as the frequency characteristic for extracting the peak or dip in this determination step, it is preferable that the impulse response waveform is Fourier transformed. Thereby, the frequency characteristic of the sound pressure level can be obtained, and the frequency of the standing wave can be specified more accurately.

As described above, the acoustic characteristic measuring method can be performed by the acoustic characteristic measuring device of FIG. 1, and the acoustic characteristic device of FIG. 1 is a programmable device having an audio input / output function such as a smartphone, a mobile computer, and a personal computer. This can be achieved by installing an acoustic characteristic measurement program. The acoustic characteristic measurement program for realizing this acoustic characteristic measuring device is itself another embodiment of the present invention.

<Acoustic characteristic measurement program>
As described above, the acoustic characteristic measurement program measures the acoustic characteristics of the audio space using a programmable device having an audio input unit (for example, a microphone terminal, a built-in microphone, etc.) and an audio output unit (for example, an earphone terminal, etc.). Program. In other words, the acoustic characteristic measurement program is a program for executing the acoustic characteristic measurement method of FIG. 2 using a programmable device.

The acoustic characteristic measurement program includes an input control element that outputs an impulse input wave from the voice output unit, a recording control element that records an impulse response waveform input to the voice input unit when the impulse input wave is output, and the impulse response waveform. It is provided with an arithmetic element for determining a frequency at which the reverberation time becomes a peak or a dip as a standing wave frequency by analyzing the above.

The input control element, the recording control element, and the calculation element may be independent programs, but it is preferable that they are subroutines, part programs, or the like that form a part of one application program. Further, it is preferable that the acoustic characteristic measurement program further includes an interface control element for setting parameters used by the calculation element for calculation.

(Input control element)
The input control element is a program element for outputting an input waveform for obtaining an impulse response, for example, a TSP (Time Stretched Pulse) signal, an M-sequence (Maximum Lens Sequence) signal, or the like, which can be output by a speaker SL or SR. Is. This input control element may provide waveform data of the impulse input wave to the operation system of the programmable device or the program element for audio output attached to the operation system.

(Recording control element)
The recording control element is a program element for recording an impulse response waveform using a voice input unit in conjunction with the input control element. That is, the input control element and the recording control element are programs for executing the acquisition step of the acoustic characteristic measurement method of FIG.

(Calculation element)
The arithmetic element is a program element for executing each step of the determination step of the acoustic characteristic measurement method of FIG. 2, that is, processing the impulse response waveform data recorded in the memory of the programmable device by the recording control element.

(Interface control element)
The interface control element displays the standing wave frequency using the display device of the programmable device. Further, it is preferable that the interface control element allows the operator to input parameters and the like used for calculation. In this case, it is preferable that the interface control element is displayed so as to facilitate the adjustment of the parameters by the operator by a method such as displaying the pulse glide figure of FIG. 4 by superimposing a line indicating the determination reference time.

<Advantage>
The acoustic characteristic measuring method device, the acoustic characteristic measuring method, and the acoustic characteristic measuring program analyze the impulse response waveform and determine the frequency at which the sound pressure level drops slowly or early as the standing wave frequency, which gives the listener a sense of discomfort. The frequency of the standing wave can be specified relatively accurately.

In this way, the frequency of the standing wave that gives the listener a sense of discomfort can be specified relatively accurately by the acoustic characteristic measuring method device, the acoustic characteristic measuring method, and the acoustic characteristic measuring program, so that the acoustic characteristic of the audio space can be determined. It can be adjusted so that a sound that does not feel strange can be reproduced. As a method of adjusting the acoustic characteristics, for example, by arranging a sound control member having a high sound absorption coefficient for a specified frequency, for example, a resonator type sound absorption member in the audio space, a standing wave having a peak sound pressure can be generated. It can be reduced.

[Other Embodiments]
The embodiments do not limit the configuration of the present invention. Therefore, it is possible to omit, replace or add components of each part of the embodiment based on the description of the present specification and common general technical knowledge, and all of them are construed as belonging to the scope of the present invention. Should be.

In the acoustic characteristic measuring method, a frequency in which the sound pressure level decrease is relatively slow or fast may be specified in the determination step by a method different from the method shown in FIG.

The acoustic characteristic measuring method, the acoustic characteristic measuring device, and the acoustic characteristic measuring program according to the present invention can be particularly preferably used for easily measuring the acoustic characteristics of a relatively small-scale audio space such as for personal use.

1 Sound generation mechanism 2 Recording mechanism 3 Calculation mechanism 4 Interface 5 Microphone 6 Recording means 7 Display means 8 Input means SL, SR Speaker S1 Acquisition process S2 Judgment process S21 Derivation process S22 Specific process S23 Determination process

Claims (9)

A method of measuring the acoustic characteristics of audio space.
The process of acquiring the impulse response waveform of a sound wave that uses an audio playback speaker as an input source at the listening point, and
It is provided with a step of analyzing the impulse response waveform and determining a frequency with a slow or fast sound pressure level drop as a standing wave frequency.
The determination step
A step of deriving a pulse glide or a cumulative phase spectrum from the impulse response waveform, and
A step of specifying a frequency at which the sound pressure level at the determination reference time is equal to or higher than the peak threshold value or lower than the dip threshold value using the pulse glide or the cumulative phase spectrum.
A method for measuring acoustic characteristics, which comprises a step of determining this frequency as a standing wave frequency.
A method of measuring the acoustic characteristics of audio space.
The process of acquiring the impulse response waveform of a sound wave that uses an audio playback speaker as an input source at the listening point, and
A step of analyzing the impulse response waveform and determining a frequency with a slow or fast sound pressure level drop as a standing wave frequency.
With
The determination step
The process of deriving the sound pressure level change for each frequency band from the impulse response waveform, and
A step of identifying a frequency band having a relatively long reverberation time or a frequency band having a relatively short reverberation time from the change in sound pressure level for each frequency band, and
Acoustics measuring method characterized by a step of determining said standing wave frequency peaks or dips in the frequency characteristic of the standing wave wherein the reverberation time as the frequency is relatively long frequency band or a short in a frequency band .. The method for measuring acoustic characteristics according to claim 2, wherein in the determination step, the impulse response waveform of the frequency band having a relatively long reverberation time or the frequency band having a relatively short reverberation time is Fourier transformed. The method for measuring acoustic characteristics according to claim 1, claim 2 or claim 3, wherein weighting is performed according to the frequency in the determination step. The acquisition process is performed separately on the left and right sides of the audio playback speaker.
The method for measuring acoustic characteristics according to any one of claims 1 to 4, wherein the standing wave frequency is determined separately on the left and right in the determination step. A device that measures the acoustic characteristics of audio space.
A sound generation mechanism that outputs an impulse input wave using an audio playback speaker,
A recording mechanism that records the impulse response waveform obtained by the impulse input wave at the listening point, and
It is equipped with a calculation mechanism that analyzes the impulse response waveform and determines a frequency with a slow or fast sound pressure level drop as a standing wave frequency.
The arithmetic mechanism
A derivation unit that derives a pulse glide or cumulative phase spectrum from the impulse response waveform, and
A frequency specifying unit that uses the pulse glide or the cumulative phase spectrum to specify a frequency at which the sound pressure level at the determination reference time is equal to or higher than the peak threshold value or lower than the dip threshold value.
An acoustic characteristic measuring device characterized by having a frequency determining unit that determines this frequency as a standing wave frequency.
A device that measures the acoustic characteristics of audio space.
A sound generation mechanism that outputs an impulse input wave using an audio playback speaker,
A recording mechanism that records the impulse response waveform obtained by the impulse input wave at the listening point, and
An arithmetic mechanism that analyzes the impulse response waveform and determines a frequency with a slow or fast sound pressure level drop as a standing wave frequency.
With
The arithmetic mechanism
A sound pressure derivation unit that derives a sound pressure level change for each frequency band from the impulse response waveform, and a sound pressure derivation unit.
A band identification unit that identifies a frequency band having a relatively long reverberation time or a frequency band having a relatively short reverberation time from the sound pressure level change for each frequency band
With a standing wave determining unit that determines a peak or dip of a frequency characteristic in a frequency band having a relatively long reverberation time or a short frequency band as the standing wave frequency as the standing wave frequency.
An acoustic characteristic measuring device characterized by having. A program for measuring the acoustic characteristics of an audio space using a programmable device having an audio input unit and an audio output unit.
An input control element that outputs an impulse input wave from the audio output section,
A recording control element that records the impulse response waveform input to the voice input unit when the impulse input wave is output, and
It is equipped with a calculation element that analyzes the impulse response waveform and determines that a frequency with a slow or fast sound pressure level drop is a standing wave frequency.
The arithmetic element is
A derivator element that derives a pulse glide or cumulative phase spectrum from the impulse response waveform, and
Using the pulse glide or the cumulative phase spectrum, a frequency specifier element that specifies a frequency at which the sound pressure level at the determination reference time is equal to or greater than the peak threshold value or equal to or lower than the dip threshold value.
An acoustic characteristic measurement program characterized by having a frequency determinant element that determines this frequency as a standing wave frequency.
A program for measuring the acoustic characteristics of an audio space using a programmable device having an audio input unit and an audio output unit.
An input control element that outputs an impulse input wave from the audio output section,
A recording control element that records the impulse response waveform input to the voice input unit when the impulse input wave is output, and
It is equipped with a calculation element that analyzes the impulse response waveform and determines that a frequency with a slow or fast sound pressure level drop is a standing wave frequency.
The arithmetic element is
A sound pressure deriver element that derives a sound pressure level change for each frequency band from the impulse response waveform, and
A band specifier element that identifies a frequency band having a relatively long reverberation time or a frequency band having a relatively short reverberation time from the change in sound pressure level for each frequency band.
It is characterized by having a standing wave determinant element that determines a peak or dip of a frequency characteristic in a frequency band having a relatively long reverberation time or a short frequency band as the standing wave frequency. Acoustic characteristic measurement program .