JPH06324689A - Acoustic measuring method - Google Patents

Abstract

PURPOSE:To precisely find the ratio (LD) of a reflected sound component from a desired side to components of sounds from all directions which are well matched with human subjective evaluation by separating and extracting the reflected sound from the desired side wall surface from a direct sound which is collected at the same time. CONSTITUTION:An impulse acoustic signal having the time base extended is collected by a unidirectional microphone 6 at a listening point so as to include at least the reflected sound from the desired side wall surface, and a computer 1 computes the impulse response of the collected signal and separates the reflected sound component from the desired side from the direct sound components in time as to the computation result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the subjective evaluation of human beings, and is an important evaluation factor for expressing room acoustic characteristics. In order to measure the ratio LC (Lateral Component) of the initial energy of the reflected sound component from
Particularly, it relates to a method of separating and extracting a reflected sound component from a desired side wall surface.

[0002]

2. Description of the Related Art A conventional method for measuring a reflected sound component from a desired side wall surface at a sound receiving point in a room is to collect sound using a parabolic microphone.
"Richtungsverteilung und Zeitfolge der Schallruckw
urfe in Raumen. "ACUSTICA, 3,291 (1953) and Meye
rE, Kuttruff.H., Roy.N. "Raumakustische Untersuch
ungen an einen Modell der Stadthalle in Gottinge
n. "ACUSTICA, 19,132 (1967), Sound collection method by dummy head Keet.V." The influence of early refrectionson
the Spatial Impression. "6th ICA, E-2-4, (1968),
So-called proximity 4-point method, Yamasuda, alley,
Yasukawa, Saito, Yamazaki, Ito: "A Method for Measuring Indoor Spatial Information Using Digital Technology" Architectural Acoustics Society of Japan Material A
A79-03 (1973), and a method of picking up sound using an array microphone, Flanagan.JL "Use of acoustic filter
ing to control the beamwidth of steered microphone
arrays. "J.Acoust.Soc.Am., 78 (2), 423 (1985), west:
"Physical evaluation of room sound field using wide-band array microphone", Acoustical Society of Japan, 44, 10, p.719 (1988) and Nishi et al .: "Multi-directional simultaneous sound pickup device", Electroacoustic workshop Material EA88-65, 33 ( 198
8) etc.

Further, although a method of collecting a reflected sound by directing a unidirectional microphone to a side wall surface has been studied so far, it is possible to accurately separate a direct sound component and a reflected sound component. Problems have been left behind (eg Mikami,
Nishi, Furukawa: "Improvement of measurement accuracy of direction information in room sound field measurement method using variable directional microphone", Proceedings of ASJ 2-8-17 (1988, Oct.)). However, since this method is also simple in principle, it can be said that the measurement equipment and the measurement method can be simplified and it is also a useful method in terms of measurement accuracy.

Furthermore, as a conventional method for obtaining the ratio of reflected sound components from the side, a method called LE (Lateral Efficiency) VL Jordan, "Acoustical Design of Concert"
Halls and Theaters "APPLIED SCIENCE PUBLISHERS (198
However, the LE has a drawback that since the reflected sound from the side is picked up by the bidirectional microphone, when the same reflected sound arrives from the left and the right, it is canceled by both. This is discussed in the above-mentioned Proceedings of the Acoustical Society of Mikami, Nishi, Furukawa 2-8-17 (1988.Oct.).

[0005]

As described in the above-mentioned prior art, a conventional method for measuring a reflected sound component from a desired side wall surface at a sound receiving point in a room and a ratio of the reflected sound components are obtained. All of the methods are unsatisfactory in that only the reflected sound component from the desired side is separated and taken out, and highly accurate measurement cannot be achieved.

The collection of the reflected sound by directing the unidirectional microphone toward a desired side wall surface has been described as the prior art, but generally at the listening point, the unidirectional microphone is directed toward the side. When collecting only the reflected sound component from the desired side, even if the microphone is directed to the side, the directivity in the sound source direction is -6 dB, and it is possible to avoid collecting the direct sound from the sound source. Absent. Therefore, a method of directly separating the sound component from the collected data has been a problem.

An object of the present invention is to collect a reflected sound by using a conventional method of collecting a unidirectional microphone toward a desired side while using a completely novel method. It is possible to accurately separate the reflected sound from the wall surface from the direct sound, thereby obtaining the ratio (LC) of the initial energy of the reflected sound component from the desired side to the component of the sound coming from all directions with high accuracy. To do so.

[0008]

In order to achieve the above-mentioned object, the acoustic measuring method of the present invention radiates an impulse acoustic signal which is time-axis expanded in a room using a speaker,
At any listening point in the room where the radiated acoustic signal is heard, a unidirectional microphone is directed toward a desired lateral wall surface and at least all reflected sound coming from the desired lateral wall surface is collected. Then, with respect to the collected acoustic signal, an impulse response regarding the impulse acoustic signal expanded in the time axis is calculated, and the direct sound from the speaker included in the collected acoustic signal and the desired sound are calculated from the calculated impulse response. It is characterized in that the reflected sound coming from the side wall surface of is separated temporally.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a system configuration diagram showing an embodiment of the acoustic measurement method of the present invention. In the present invention, as seen in this example, an actual sound is produced using a speaker in a room such as a hall to be measured, and an acoustic signal in which a direct sound and a reflected sound from a desired side wall surface are mixed is generated. The unidirectional microphone collects sound and processes the waveform to separate and measure the reflected sound from the desired side.

In FIG. 1, a data signal (TSP (Time Stretch
ed Pulse) signal data) is output. This signal is D /
The signal is converted into an analog signal by the A converter 2, and is further applied to the speaker 5 installed in the hall 9 through the analog filter 3 and the amplifier 4 for achieving the desired band characteristic and level determined by the measurement conditions and the like.

In the hall 9, the acoustic signal radiated from the speaker 5 is picked up by the microphone 6 arranged at the position corresponding to the listening point. This microphone 6
Has a unidirectional directivity so that a sound reflected from a desired side wall surface can be collected.

In the embodiment shown in the figure, in order to obtain unidirectionality by phase combination, a total of five omnidirectional microphones, which are composed of four peripherally arranged symmetrically with respect to one at the center, are provided. Use two of these four omnidirectional microphones to create bidirectional patterns, and combine them with one remaining omnidirectional microphone to obtain unidirectionality in all directions by directivity synthesis. To this is,
This is because the reflected sound from any direction can be easily measured without changing the direction of the microphone. By collecting the sound using the microphone having the desired directivity in this way, the reflected sound coming from the desired side can be collected. However, the picked up sound naturally includes not only a desired side sound but also a direct sound.

The picked-up acoustic signal (electrical signal) is amplified by the amplifier 7, converted into digital data (response data) through the A / D converter 8 and taken into the post-computer 1. Waveform processing is performed in the computer 1 based on the sound pickup result of the impulse sound whose time axis has been expanded as the response data taken in, and the lateral impulse response at the listening point in the room where the sound is picked up is calculated. At the same time, the response by sound from all directions including the direct sound picked up by one central omnidirectional microphone among the above-mentioned five omnidirectional microphones is also calculated.

FIG. 2 shows the result of calculating the impulse response based on the data obtained by collecting the sound with the directivity of the microphone set to the desired side. As described above, even when the directivity of the microphone is set to the side, the collected sound also has a direct sound component. However, since it is an impulse response, the rising and falling edges of the direct sound component are sharp, and it is easy to distinguish it from the reflected sound component.
As shown by the broken line, when the level of the direct sound component is sufficiently low, the waveform is cut in time and the direct sound component is separated and removed from the impulse response, so that only the reflected sound component is responded. Enable to record as data.

As described above, it becomes possible to separate and extract only the reflected sound that reaches the listening point from the desired side for the purpose of the present invention. However, using the reflected sound from this side,
For the components of the sound that arrive at the listening point from all directions,
The ratio (LC) for the initial energy of about 0 to 80 msec can be calculated by the following formula.

[Equation 1]

[0016]

According to the present invention, the method of collecting the reflected sound from a desired side wall surface such as a hall by using a unidirectional microphone as in the conventional method, The impulse sound signal with time-axis extension is radiated from the speaker, and at the listening point, a unidirectional microphone is used to collect at least the reflected sound coming from the desired side wall surface, and the collected sound is collected. Since the impulse response of the signal is obtained and the direct sound component and the reflected sound component are temporally separated, the reflected sound coming from the desired side wall surface can be accurately measured.

Further, according to the present invention, since only the reflected sound component from the side can be reliably collected, the side of the sound component arriving from all directions of the initial energy at the listening point is detected. Ratio of reflected sound component from (LC)
Is required with high accuracy. Up to now, a number of microphones have been used, the direction of arrival of the sound has been measured from the phase difference of the individual microphones, and the reflected sound from the side has been collected. In the invention, since the unidirectional microphone is measured directly toward the side, the number of measuring equipment is small and the measurement itself is simple in principle, so that the reflected sound from the side can be easily measured. In this measurement, even if several synchronous additions are taken, it is expected that the LC can be calculated in about 10 to 15 minutes at one measurement point.

Further, in the impulse response output as the measurement result, the time from the rising to the falling of the direct sound component is about 20 μsec (at the time of sampling at 48 kHz), but the direct sound component is first received. It is considered that it usually takes about 5 to 10 msec (in a medium-sized hall) until the reflected sound component arrives. Therefore, the direct sound component and the reflected sound component can be sufficiently distinguished in terms of time. The component and the reflected sound component can be accurately separated. As a result, the impulse response due to the sound components coming from all directions measured at the same time,
Since each result of the impulse response, which is separated and has only the reflected sound component from the side, can be used, L
C can be obtained with higher accuracy, which is useful for measurement and evaluation of room acoustics.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of an acoustic measurement method according to the present invention.

2 is a diagram showing the impulse response calculated in the system of FIG.

[Explanation of symbols]

 1 Calculator 2 D / A converter 3 Analog filter 4,7 Amplifier 5 Speaker 6 Microphone 8 A / D converter 9 Hall

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Itsuo Tanabe 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory (72) Inventor Takashi Nishi 1-10-11 Kinuta, Setagaya-ku, Tokyo Issue Broadcasting Technology Research Institute, Japan Broadcasting Corporation

Claims (1)

[Claims] 1. A unidirectional microphone is radiated in a desired lateral direction at an arbitrary listening point in a room where a time-axis-extended impulse acoustic signal is radiated using a speaker and the radiated acoustic signal is heard. Reflected sound coming from the desired side wall toward the wall surface is collected so as to include at least all, and for the collected sound signal, an impulse response regarding the impulse sound signal expanded in the time axis is calculated, and An acoustic measuring method characterized in that a direct sound from the speaker and a reflected sound coming from the desired lateral wall surface, which are included in the collected acoustic signal, are temporally separated from the calculated impulse response. .