JP2539672B2 - Audio playback method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a voice reproduction system for reducing the listening range where the conversation content of reproduced voice can be understood.

“Conventional technology” When implementing communication conference systems such as voice conferences and video conferences, the playback device is often used for a long time due to the nature of the conference, and using a handset or earphones puts a heavy burden on the listener. The first problem of causing a feeling of pressure and a feeling of pressure occurs.

On the other hand, a method of using a loudspeaker without using a receiver or earphones is conceivable, but has a drawback that is not regarded as a problem with the receivers or earphones. That is, when a communication conference is held in an environment in which people (non-parties) unrelated to the conference are present, a second problem arises in that the content of the reproduced conference is heard by the non-party.

In order to deal with this point, a method of giving directivity to the loudspeaker can be considered. It utilizes the fact that it is difficult for non-parties unrelated to the conference to listen if only the parties are located within the listening range reduced by the directivity. By the way, the frequency band for faithful reproduction of voice is considered to be 100 Hz to 8000 Hz, which is a human vocal range. In order to give the directivity of the loudspeaker to the low frequency range of 100Hz, it is necessary to make the speaker diameter about 1 m or more from the relationship between the wavelength and the speaker diameter. For this reason, the third problem arises in that the loudspeaker becomes large and the economical efficiency is reduced.

In addition, since a speaker that reproduces sound in the frequency band of 100 Hz to 8000 Hz is usually designed to spread uniformly in the listening space regardless of the frequency band, there is a fourth problem that the conventional speaker cannot be used as it is. .

An object of the present invention is to reduce the listening range in which the conversation content of the reproduced voice can be understood and to prevent non-parties from listening, and to eliminate the above-mentioned conventional drawbacks, the intelligibility of the conversation content is affected. It is an object of the present invention to provide an audio reproducing system in which a directional speaker reproduces a frequency band that gives a noise, and an omnidirectional speaker reproduces other frequency bands.

[Means for Solving the Problems] According to the present invention, a frequency band having directivity and a frequency band having no directivity when reproducing an input audio signal are set, and An audio signal in the frequency band that gives directivity is extracted, and the audio signal is reproduced by a directional speaker,
An audio signal in a frequency band having no directivity is extracted from the input audio signal and the audio signal is reproduced by the omnidirectional speaker.

In Japanese conversation, vowels are often used, and the formant frequency band, which is a component sound that characterizes the five Japanese vowels, is known. Of these, if a certain formant frequency band is removed, there is a phenomenon that the vowel becomes inaudible. Makita et al., "Present Acoustics" (Ohmsha, 1976, p. 55)
According to the literature, audible vowel "a" is 2000Hz, vowel "d" is 1700Hz, vowel "a" is 800Hz and 1200Hz, vowel "o" is 500Hz, and vowel "u" is 300Hz. It is known that the vowel becomes inaudible when the band of is removed. Therefore, by removing these bands in combination, it is possible to appropriately reduce the intelligibility of the conversation content.

The present invention divides a frequency band into two, for example, by utilizing the above-mentioned auditory property, and band-dividing into a formant frequency band of interest (including frequencies in the vicinity thereof) and other frequency bands, and the former frequency is used. The sound in the band is reproduced from the directional speaker, and the sound in the latter band is reproduced from the omnidirectional speaker.

"Embodiment" FIG. 1 is a first system example showing the features of the present invention. The frequency division circuit 11 divides the frequency band of the monaural sound audio signal transferred from the input terminal 10, and reproduces the sound of the formant frequency of interest (including frequencies in the vicinity) from the directional speaker 12. , Voices of other frequencies are reproduced from the omnidirectional speaker 13. The directional speaker 12 has a conversation content 14
The omnidirectional speaker 13 has a role of allowing the parties 15 to hear without hearing (without being understood).
It has the role of giving a sense of thickness. The party 15 is a speaker
The sound of 12 and the speaker 13 is heard, and the non-party 14 hears only the sound of the speaker 13.

FIG. 2 is a second system example showing the features of the present invention. With respect to the stereo audio signals (L signal and R signal) transferred from the input terminal 10, the L signal and the R signal respectively follow the reproduction operation described in FIG. Of the frequency band, and these are divided into the L signal directional speaker 12L, the L signal omnidirectional speaker 13L, and the R signal directional speaker 1.
It is reproduced from the 2R and R signal omnidirectional speaker 13R. The party 15 can hear the conversation content by sound localization.

In the conventional technology, the speaker tends to be large in size because the directivity is given to all frequency bands, but in the present invention, the directivity is increased with respect to the frequency band that affects the intelligibility of the conversation content. This is a big difference from the conventional one.

FIG. 3 shows an embodiment of the present invention. The input terminal 10 is connected to the directional band extraction / playback unit 21 and the omnidirectional band extraction / playback unit 22, the output side of the directional band extraction / playback unit 21 is connected to the directional speaker 12, and the omnidirectional band extraction / playback unit is connected. The output side of 22 is connected to the omnidirectional speaker 13. The directional band extracting / reproducing unit 21 and the omnidirectional band extracting / reproducing unit 22 are also connected to the frequency band setting unit 23. Further, the directional band extraction / reproduction unit 21, the omnidirectional band extraction / reproduction unit 22, and the frequency band setting unit 23 are connected to the control unit 24.

To operate this, in response to a command from the control unit 24, the frequency band setting unit 23 sets the directional band setting data and the omnidirectional band setting data that are predetermined in consideration of the male voice, the female voice, the sound effect of conversation, and the like. Are transmitted to the directional band extracting / reproducing unit 21 and the omnidirectional band extracting / reproducing unit 22, respectively. The directional band extracting / reproducing unit 21 performs initial setting based on the directional band data, and after completion of setting, transfers the completion notification to the frequency band setting unit 23. At the same time, the omnidirectional band extraction / reproduction unit 22 performs initial setting based on the omnidirectional band data, and after completion of the setting, transfers the completion notification to the frequency band setting unit 23.
The frequency band setting unit 23 receives the completion notification received from the directional band extraction / playback unit 21 and the completion notification received from the omnidirectional band extraction / playback unit 22, and then issues an activation start command to the directional band extraction / playback unit. 21 and the omnidirectional band extraction / playback unit 22 are notified. After the notification is completed, the directional band extraction / playback unit 21
Extracts only the band of the voice initially set for the audio signal sent from the input terminal 10 and reproduces the voice through the directional speaker 12. Similarly, the omnidirectional band extraction / reproduction unit 22 extracts only the initially set audio band and reproduces the audio through the omnidirectional speaker 13.

The directional speaker 12 includes a magnet 31, a voice coil 32, and a cone.
33, the omnidirectional speaker 13 includes a magnet 34, a voice coil 35, and a cone 36 on the outside of the front of the directional speaker 12. As described above, the acoustic lens 37 that converges to the structure in which the directional speaker 12 and the omnidirectional speaker 13 are overlapped is housed in the cabinet 38 to reduce the size of the speaker.

FIG. 5 shows a second specific example of the speaker configuration. The directional speaker 12 and the omnidirectional speaker 13 are arranged in a cabinet 38. In order to provide directivity, the directional speaker 12 has a speaker diameter designed based on the wavelength of the lowest frequency among the directional frequencies. The omnidirectional speaker 13 is designed to be able to reproduce all set omnidirectional frequencies.

In addition, the directional speaker 12
It is described that the reproduction is performed separately for the omnidirectional speaker 13 and the omnidirectional speaker 13, but the sound of all frequency bands is output to the omnidirectional speaker 13 and only the sound of the focused formant frequency band is output to the directional speaker 12. Methods are also included in the invention. This method has the effect of increasing the energy of the voice in the formant frequency band of interest to the party 15 and making it easier to hear. Further, although the band division of omnidirectionality and directivity has been described above with reference to the formant frequency, directivity may be provided only in the frequency band in which an individual can be discriminated from the timbre of the voice.

[Advantages of the Invention] As described above, according to the voice reproduction method of the present invention, a directional speaker is provided for voices in the formant frequency band (including frequencies in the vicinity thereof) that affect the intelligibility of conversation content. Is played back via the omnidirectional speaker for audio in other frequency bands, which is advantageous for the listener to be hands-free, and the conversation content can be heard only by the parties concerned. It has the advantage that it is inaudible to non-parties. Furthermore, since the directivity is not given to all frequencies in the human vocal range of 100 Hz to 8000 Hz, the directivity is given only to some frequency bands of 300 Hz to 2000 Hz in the middle range. There is an advantage that the size can be reduced and the economy can be improved. There is also an advantage in that the use of an omnidirectional speaker can provide a feeling of sound spread and a feeling of thickness.

Further, since the directivity is given to the frequency band in which an individual can be discriminated from the timbre of the sound, there is an advantage that the surrounding non-parties cannot know who the other party is in addition to the conversation content.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first system example showing the features of the present invention, FIG. 2 is a block diagram showing a second system example showing the features of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a block diagram showing the configuration, FIG. 4 shows a first specific example of the speaker configuration, A is a perspective view, B is a sectional view, and FIG. 5 is a perspective view showing a second specific example of the speaker configuration.

Claims (1)

(57) [Claims] 1. A voice reproduction system having a speaker having directivity and a speaker having non-directivity, wherein a frequency band and a directivity for giving directivity when reproducing an input audio signal are provided. Means for setting a frequency band that does not have, means for extracting an audio signal in the frequency band having directivity from the input audio signal and reproducing the audio signal using the directional speaker, and directing from the input audio signal Means for extracting an audio signal in the frequency band having no property and reproducing it using the omnidirectional speaker.