JP2014068117A - Signal amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal amplifier for driving a speaker array capable of solving a problem that, when the volume of input signal is small, mainly low band is masked due to the influence of background noises in a reproduction sound field.SOLUTION: The signal amplifier for outputting input signals to plural speaker disposed in an array includes: a distribution section that equally divides an input signal into two and outputs the same therefrom; a compensation frequency band determination section that determines compensation frequency band which is a frequency band masked by the background noises and a compensation sound pressure level used for amplifying the signals included in the compensation frequency band; and a signal amplifying section that performs gain amplification on the signals included in the compensation frequency band in one input signals output from the distribution section based on the compensation sound pressure level. The distribution section outputs input signals to a part of the plural speakers. The signal amplifying section outputs amplified input signals to the rest speakers.

Description

  The present invention relates to an acoustic signal processing technique using a signal amplifying device that drives a speaker array in which a plurality of speakers are arranged, and more particularly, a function that realizes wideband reproduction by compensating a low frequency band masked by background noise. And a sound signal processing method.

  The speaker array is a system in which a plurality of speaker units are arranged close to each other in a straight line and operated as a linear sound source. This system has the following features. While ordinary speakers have unique radiation characteristics, they are close to point sound sources that spread sound both horizontally and vertically, whereas speaker arrays operate as linear sound sources with multiple speakers in a straight line. Can be made. In addition to this feature, by using phase interference according to acoustic theory, signals can be emitted more strongly in front of the speaker array, and as a result, sound clarity can be improved even in reverberant spaces It becomes. Furthermore, compared with a normal speaker (point sound source), the speaker array (linear sound source) has less attenuation of sound due to the distance, and can reduce the volume difference between a location near and far from the speaker array. Further, since the sound distance attenuation is small, the acoustic energy of the input signal to each speaker constituting the speaker array can be small, and as a result, the output of the amplifier can be reduced.

  Taking advantage of these characteristics, the speaker array in the prior art is output from each speaker by turning off the output of some amplifiers and reducing the number of speakers that reproduce the input signal when reproducing at a low volume. The attenuation of the sound pressure mainly in the high range, which is caused by the phase interference of each signal, is reduced. As a result, the sound pressure attenuation in the high range is mainly smaller than when the amplification factor of the amplifier is reduced and output using all speakers, and it is possible to output sound in a wide frequency band (patent) Reference 1).

JP 2008-67041 A

  However, when playing back at a low volume, the playback band is compensated for high-frequency audio signals. However, because the volume is low, the low frequency is masked due to the influence of background noise, resulting in a low level. It becomes difficult to hear the sound of the area. Since no countermeasure has been taken against such a problem, there is a problem that wide-band reproduction has not been sufficiently realized.

  The present invention solves the above-described conventional problems, and realizes wideband reproduction by compensating the low frequency range of the input signal according to the background noise level when reproducing at a low volume in the signal amplification device that drives the speaker array. An object of the present invention is to provide a signal amplifying device.

  In order to solve the above-described conventional problems, a signal amplifying device according to one aspect of the present invention is a signal amplifying device that outputs a reproduction signal from a plurality of speakers arranged in an array. A frequency band for compensating when one of the input signals distributed by the distribution unit is lower than a background noise level, a compensation frequency band determining unit for determining a compensation sound pressure level, and the compensation frequency band A signal amplifying unit that amplifies the gain by the compensation sound pressure level with respect to the frequency band determined by the determining unit, and the signal amplified by the signal amplifying unit and the other input signal distributed by the distributing unit; Are reproduced from the speaker array, and a certain frequency band reproduced from some of the plurality of speakers is larger than the background noise level. Masking no longer occur in order to be reproduced in sound pressure level, resulting in a possible broadband reproduction.

  In the invention according to claim 2 of the present application, in the compensation frequency band determining unit in the signal amplifying device according to claim 1, a frequency band reproduced from some of the plurality of speakers is the input signal. The reproduction signal is generated so as to increase toward the high frequency side as the volume decreases.

  According to the present invention, the signal amplifying device avoids masking and realizes wideband reproduction in the reproduction sound field by compensating only for the low frequency masked by the background noise when reproduced at a low volume. Can do.

FIG. 1 is a block diagram showing the configuration of the signal amplifying apparatus according to the present embodiment. FIG. 2 is a flowchart showing an example of the operation of the signal amplifying apparatus according to the present embodiment. FIG. 3 is a diagram showing a general background noise level in the frequency domain. FIG. 4 is a diagram illustrating an example when the input signal and the background noise level in the frequency domain of the present embodiment cross each other. FIG. 5 is a diagram illustrating a state in which the sound pressure level of a specific band in the input signal of the present embodiment is amplified. FIG. 6 is a diagram illustrating an example when the input signal and the background noise level do not cross in the frequency domain according to the present embodiment.

(Embodiment)
Hereinafter, the present embodiment will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the signal amplifying apparatus according to this embodiment.

  The signal amplification device according to the present embodiment includes a distribution unit 1, a compensation frequency band determination unit 2, and a signal amplification unit 3. The signal amplifying device is connected to the speaker array 4 outside or inside.

  In the signal amplifying apparatus, of the two input signals equally distributed by the distribution unit 1, the signal processed by the input signal processing unit 100 is reproduced by m speakers out of (m + n) speakers 4, and By reproducing one of the signals with n speakers, the low frequency range of the input signal can be compensated according to the background noise level, and broadband reproduction is possible.

  The distribution unit 1 acquires an audio signal input from the outside. The distribution unit 1 acquires an audio signal recorded on, for example, a DVD. In addition, the distribution unit 1 acquires an audio signal via a network. That is, the distribution unit 1 only needs to have a function of acquiring an audio signal, and any acquisition path may be used.

  Furthermore, the distribution unit 1 distributes the acquired audio signal. Then, the distributing unit 1 outputs two signals obtained by distributing the audio signal to the compensation frequency band determination part 2 and the speaker array 4.

  The compensation frequency band determination part 2 determines a compensation frequency band where the audio signal and the background noise cross. Specific operations will be described later.

  The signal amplifying unit 3 multiplies the audio signal in the compensation frequency band determined in the compensation frequency band determination part 2 by a gain and outputs the result. The speaker array 4 outputs an audio signal obtained by multiplying some of the connected speakers by a gain.

  The speaker array 4 reproduces an audio signal output from the distribution unit 1 or the signal amplification unit 3. The speaker array 4 includes SP1 to SPm + m. The listener can arbitrarily select m speakers that reproduce low frequencies. In addition, the number of speakers that reproduce audio signals over all frequency bands is (n + m).

  The signal amplifying apparatus configured as described above will be described in detail below.

  FIG. 2 is a flowchart illustrating an example of an operation when the input signal distributed by the distribution unit 1 is processed by the input signal processing unit 100. The distribution unit 1 distributes the input signal equally into two signals (S11). Next, the compensation frequency band determination unit 2 converts the input signal into frequency domain data by FFT, and determines the frequency at which the input signal and the background noise level cross (S12). Here, in the frequency domain, the background noise level is generally higher as the frequency is lower as shown in FIG. 3, for example, and is lower as the frequency is higher. When the sound pressure level of a certain signal is smaller than the background noise level, that is, when a band having a frequency amplitude response of the input signal reaches the shaded portion in FIG. 3, the input signal is masked by the background noise. As a result, the sound in the band cannot be heard. Here, since the background noise level measured by the microphone and the sound pressure level of the input signal are different and cannot be compared as they are, the value obtained by converting the background noise level according to the sound pressure level scale is used below. . In the present embodiment, a description will be given below using a general background noise level as shown in FIG. 3, but the background noise levels of various spaces assumed in advance are stored in a table so that the user can The background noise level used arbitrarily may be selected, or the background noise level in the space where the signal amplifier for driving the speaker array in the present invention is installed is measured and used in real time by measuring the sound field using a microphone. May be.

  FIG. 4 is a diagram illustrating a state in which the background noise level and the input signal cross each other. In the figure, Xth [Hz] is a lower limit frequency arbitrarily set for the compensation frequency band, and the background noise level at that frequency is Yth [dB]. Xth [Hz] may be set to 20 [Hz], which is the lowest audible frequency of humans, for example. The crossing frequency is X [Hz] (X> Xth) from the intersection of the input signal and the background noise level, and the compensation frequency band to be compensated for the low frequency is (Xth to X) [Hz from the frequency crossing the lower limit frequency. ] Is determined. When the sound pressure level of the input signal at the lower limit frequency Xth [Hz] is Y (Yth> Y), the compensation sound pressure level necessary to avoid masking in the compensation frequency band of the input signal is (Yth−Y) [ dB]. That is, if the sound pressure level is increased by the compensation sound pressure level (Yth−Y) [dB] with respect to the compensation frequency band, masking does not occur.

  Next, the signal amplifying unit 3 amplifies the sound pressure level of the determined compensation frequency band (Xth to X) [Hz] by the compensation sound pressure level (Yth−Y) [dB] in the input signal, and performs IFFT. Output to m speakers (S13). As a means for amplifying, a means for amplifying the level of a specific frequency band, such as an equalizer, can be considered.

  As described above, among the input signals equally distributed by the distribution unit 1, signals amplified in a specific band by the input signal processing unit 100 are used as (m + n) speakers 4 constituting the speaker array. Among them, by reproducing from m speakers and reproducing the other signal from the remaining n speakers, the sound pressure level of the input signal is conventionally lower than the background noise level. Signals that could not be heard by masking become audible, and as a result, wideband reproduction is possible.

  As shown in FIG. 6, in the compensation frequency band determining unit 2, when the input signal is larger than the background noise level in all bands, that is, when the frequency response of the input signal does not cross the background noise level, masking does not occur. The signal amplifier 3 does not need to amplify the signal and outputs the input signal to the speaker as it is. That is, the respective signals equally distributed into two by the distribution unit 1 are output to (m + n) speakers without any processing.

  The present invention can be applied to a device that can reproduce an audio signal and includes a device that drives two or more plural speakers, and is particularly applicable to a speaker array device.

DESCRIPTION OF SYMBOLS 1 Distribution part 2 Compensation frequency band determination part 3 Signal amplification part 4 Speaker array

Claims (2)

A signal amplifying apparatus that outputs input signals to a plurality of speakers arranged in an array,
A distribution unit that equally distributes the input signal to two and outputs the two;
A compensation frequency band determining unit for determining a compensation frequency band that is a frequency band masked by background noise and a compensation sound pressure level used when amplifying the signal belonging to the compensation frequency band;
A signal amplification unit that performs gain amplification based on the compensation sound pressure level for a signal belonging to the compensation frequency band among the one input signal output by the distribution unit;
The distribution unit outputs an input signal to some of the plurality of speakers, and the signal amplification unit outputs an amplified input signal to the remaining speakers.   The compensation frequency band determining unit generates a reproduction signal such that a frequency band reproduced from some of the plurality of speakers becomes wider toward the high frequency side as the volume of the input signal decreases. The signal amplification device according to claim 1.

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