Sound field measurement device

• US 20040240676A1
• Filed: 05/25/2004
• Published: 12/02/2004
• Est. Priority Date: 05/26/2003
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Hashimoto, Hiroyuki, Hashimoto, Koichi, Satoh, Kazue, Terai, Kenichi
• Granted Patent: US 7,680,286 B2
• Time in Patent Office: Days
• US Class Current: 381/56
• CPC Class Codes: H04R 2499/13 Acoustic transducers and sound field adaptation in vehicles
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers
• CPC Class Codes: H04S 7/301 Automatic calibration of stereophonic sound system, e.g. with test microphone
• CPC Class Codes: H04S 7/302 Electronic adaptation of stereophonic sound system to listener position or orientation H04S7/301 takes precedence
• CPC Class Codes: H04S 7/305 Electronic adaptation of stereophonic audio signals to reverberation of the listening space H04S7/301 takes precedence
• CPC Class Codes: H04S 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence

Abstract

A wide frequency range signal from a test sound source 1 is reproduced successively by a plurality of speakers 101 to 104, and the reproduced sound is detected by a plurality of microphones 111 and 112, after which the frequency characteristics thereof are obtained at FFTs 4b and 4c, while obtaining the frequency characteristics of the wide frequency range signal at an FFT 4a. A high frequency range level is normalized with a low frequency range level, and a determination section 8 compares the normalized value with a reference value stored in a reference value storage section 9 to determine the number and positions of people in the sound field. At the same time, the transfer functions between the speakers and the microphones are calculated at transfer function calculators 10a and 10b, and impulse responses are obtained at IFFTs 12a and 12b, after which a reverberation time calculator 13 calculates the reverberation time based on the impulse responses. An audio signal is adjusted based on the results obtained from the determination section 8 and the reverberation time calculator 13, whereby it is possible to optimize the audio reproduction according to changes in the sound field.

Claims

1. A sound field measurement device, comprising:

a test sound source for generating a signal;

a plurality of speakers for reproducing the signal from the test sound source to output test sound;

a plurality of microphones for detecting the test sound outputted from the plurality of speakers; and

a measurement section for determining the number and positions of people present in a sound field or calculating a reverberation time of the sound field, based on test sound signals detected by the plurality of microphones.

2. The sound field measurement device according to claim 1, further comprising a directionality controller for changing a directionality of the plurality of microphones in connection with a position of the speaker outputting the test sound.

3. The sound field measurement device according to claim 1, wherein the test sound source generates at least a signal in a high frequency range, and the measurement section includes:

a frequency analyzer for analyzing frequency characteristics of each of the test sound signals detected by the plurality of microphones;

a level calculator for calculating a level of each test sound signal based on the analysis by the frequency analyzer;

a reference value storage section storing a reference value; and

a determination section for comparing a level value of each test sound signal obtained by the level calculator with the reference value stored in the reference value storage section to determine the number and positions of people present in the sound field.

4. The sound field measurement device according to claim 1, wherein the measurement section includes:

a frequency analyzer for analyzing frequency characteristics of each of the test sound signals detected by the plurality of microphones and frequency characteristics of a signal from the test sound source;

a transfer function calculator for calculating a transfer function for each of the test sound signals based on the analysis by the frequency analyzer;

an impulse response calculator for calculating an impulse response for each transfer function based on the transfer function calculated by the transfer function calculator; and

a reverberation time calculator for calculating a reverberation time of the sound field for each impulse response based on the impulse response calculated by the impulse response calculator.

5. The sound field measurement device according to claim 3, further comprising an audio signal adjustment section for adjusting at least one of a sound image, a tone quality and a volume of an audio signal based on the number and positions of passengers as determined by the determination section.

6. The sound field measurement device according to claim 4, further comprising an audio signal adjustment section for adjusting a sound field of an audio signal based on the reverberation time calculated by the reverberation time calculator.

7. The sound field measurement device according to claim 1, wherein a signal from the test sound source is one of an impulse signal, a random signal such as white noise or pink noise, a sweep pulse signal, a music signal, and a series of musical tones including a piano scale or a plurality of chords.

8. The sound field measurement device according to claim 1, wherein the plurality of speakers successively reproduce the signal from the test sound source while taking turns at a predetermined time interval determined according to the signal.

9. The sound field measurement device according to claim 1, wherein the plurality of speakers are installed in doors of an automobile inside a cabin of the automobile.

10. The sound field measurement device according to claim 1, wherein at least two of the plurality of microphones are installed either on a cabin ceiling near a center of a cabin of an automobile, on top of a seat back of a driver'"'"'s seat or a front passenger'"'"'s seat near the center of the cabin, around the sun visor of the driver'"'"'s seat inside the cabin, or around the rear-view mirror inside the cabin.

11. The sound field measurement device according to claim 2, wherein the directionality controller processes signals from at least three of the plurality of microphones so that a directionality of the microphones is strengthened in a direction toward the speaker outputting the test sound.

12. The sound field measurement device according to claim 11, wherein:

the plurality of speakers are at least four speakers including a front-right speaker, a front-left speaker, a rear-right speaker and a rear-left speaker;

one microphone is positioned at an intersection between a straight line between the front-right speaker and the rear-left speaker and another straight line between the front-left speaker and the rear-right speaker; and

two microphones other than said one microphone are positioned along the two straight lines, one on each straight line.

13. The sound field measurement device according to claim 1, wherein the reference value storage section stores, as the reference value, transfer characteristics between each speaker-microphone pair in the absence of people in the sound field, or transfer characteristics between each speaker-microphone pair for each of possible combinations of positions of people in the sound field including the absence of people therein.

14. The sound field measurement device according to claim 3, wherein:

the test sound source outputs a wide frequency range signal or outputs a high frequency range signal and a low frequency range signal in a time division manner;

the measurement section further includes a high frequency range level calculator and a low frequency range level calculator for calculating a high frequency range signal level and a low frequency range signal level, respectively, of each of the test sound signals detected by the plurality of microphones based on the analysis by the frequency analyzer; and

the determination section determines where a person is present or absent by comparing a normalized value with the reference value stored in the reference value storage section, the normalized value being obtained by normalizing a level value in a predetermined portion of a high frequency range from the high frequency range level calculator with a level value in a predetermined portion of a low frequency range from the low frequency range level calculator.

15. The sound field measurement device according to claim 14, wherein the reference value is obtained by normalizing a level value in a predetermined portion of a high frequency range from the high frequency range level calculator in the absence of people in the sound field with a level value in a predetermined portion of a low frequency range from the low frequency range level calculator in the absence of people in the sound field.

16. The sound field measurement device according to claim 1, wherein the determination section determines the presence/absence of a person at a position based on test sound signals detected by the plurality of microphones when a speaker located close to the position outputs the test sound.

17. The sound field measurement device according to claim 5, wherein based on the number and positions of passengers determined by the determination section, the audio signal adjustment section controls at least one of an input distributor for distributing a plurality of channels of audio signal among the speakers, a tone quality adjustment section for individually adjusting a tone quality of each channel of audio signal, and a sound image controller for individually controlling a sound image of each channel of audio signal.

18. The sound field measurement device according to claim 6, wherein the audio signal adjustment section adjusts the sound field of a plurality of channels of audio signal by adding early reflections and reverberations to each channel of audio signal according to the reverberation time calculated by the reverberation time calculator.

19. The sound field measurement device according to claim 5, further comprising a noise level calculator for calculating a noise level in the sound field based on signals from the plurality of microphones,

wherein the audio signal adjustment section varies a volume of an audio signal, or varies an audio signal level in a frequency range where the audio signal is masked by the noise, according to the calculated noise level.

20. The sound field measurement device according to claim 6, further comprising a noise level calculator for calculating a noise level in the sound field based on signals from the plurality of microphones,

wherein the audio signal adjustment section varies a volume of an audio signal, or varies an audio signal level in a frequency range where the audio signal is masked by the noise, according to the calculated noise level.

21. The sound field measurement device according to claim 5, wherein the audio signal adjustment section adjusts a sound field, a sound image, a tone quality, a reverberation time or a volume of an audio signal by using at least one of sources of information available from an automobile, including a calendar, a clock, a light ON/OFF state signal, a thermometer, a hygrometer, a wiper operation signal, a speedometer, a tachometer and a navigation system.

22. The sound field measurement device according to claim 6, wherein the audio signal adjustment section adjusts a sound field, a sound image, a tone quality, a reverberation time or a volume of an audio signal by using at least one of sources of information available from an automobile, including a calendar, a clock, a light ON/OFF state signal, a thermometer, a hygrometer, a wiper operation signal, a speedometer, a tachometer and a navigation system.