JP5495677B2 - Impulse sound source and reverberation time measurement method - Google Patents

Description

  The present invention relates to an impulse sound source used for measuring reverberation time in a concert hall or a studio, and a reverberation time measuring method using the impulse sound source.

Reverberation time measurement is not limited to sound fields that emphasize acoustic performance, such as concert halls and studios, but is also intended to know the sound-absorbing state of the sound receiving side even in general rooms that are subject to sound insulation and floor impact sound performance measurement. There are many opportunities that are needed. For example, in a conference room with a long reverberation time, it is difficult to hear the content of the talk, so it is necessary to measure the reverberation time.

As a method for measuring the reverberation time, a noise of 10 or more seconds is radiated sequentially from a large dodecahedron speaker, etc., and the sound attenuation process from the time when the radiation is suddenly stopped until the background noise level is observed (noise) (Intermittent method) is known, and a large-sized speaker is moved per room and a plurality of measurements are performed. Further, as a simple reverberation time measurement, a method using an impulse sound source is known, and measurement is performed at a plurality of locations per room. As simple impulse sound sources, starter pistols for athletics, crackers (powder firing sound) and balloons (plosive sound) are used. In addition, the sound of clapping hands and hitting sounds from belts are used.

However, starter pistols for athletics are in the shape of pistols and use gunpowder, so they may not be able to be brought in depending on the transportation and are cumbersome to handle. Moreover, the explosive for the number of times of measurement is necessary. A cracker is similar to a starter pistol for athletics and is not easy to use. In addition, the balloon must be inflated each time it is measured, and it is very difficult to inflate to a certain state, so it cannot be adopted as a stable sound source. The hitting sound of a clapping hand or a belt has few low frequency components and it is difficult to obtain a sufficient sound pressure.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide an impulse sound source and a reverberation time measurement method for generating an impulse sound with a simple and stable impulse waveform. Is to provide.

  In order to solve the above-mentioned problem, the invention according to claim 1 includes a sound generating unit having a structure on one side of a paper gun, and swings down the sound generating unit to generate a single impact sound for measuring the reverberation time in the room. Is.

In addition, a support member (4) for supporting the structure on one side of the paper gun can be provided on the fold (2b) serving as an opening / closing axis of the paper gun.

The invention according to claim 2 is a method for measuring the reverberation time in a room, wherein an impulse sound is generated by the impulse sound source according to claim 1, and an impact sound generated in the impulse sound generation step. The impulse response measurement step for measuring the impulse response by the step, the impulse sound generation step and the impulse response measurement step are repeated a predetermined number of times, and the reverberation time is calculated by the impulse response integration method from the impulse response measured in this repetition step. It consists of a reverberation time calculation step.

According to the first aspect of the present invention, it is possible to generate an impulse sound with a stable and good reproducibility, which is inexpensive, easy to carry and can be used repeatedly.

Further, if a support member for supporting the structure on one side of the paper gun is provided at the fold serving as the opening / closing axis of the paper gun, it is possible to generate an impulse sound with an impulse waveform with reduced variation by the operator.

According to the second aspect of the present invention, it is possible to generate an impulse sound having an impulse waveform with less tailing compared to a cracker or a balloon, so that the reverberation time measurement accuracy is improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the impulse sound source which concerns on this invention, (a) is the state before emitting an impact sound, (b) is the state after emitting an impact sound. It is an external view of another embodiment of the impulse sound source according to the present invention, (a) when the support member is disposed inside the fold, (b) when the support member is disposed outside the fold Dimensional drawing of paper gun FIG. 4 is a diagram showing the maximum sound pressure levels of various sound sources, where (a) is an impulse sound source according to the first embodiment of the present invention, (b) is an impulse sound source according to the second embodiment of the present invention, and (c) is a cracker If (d) is a balloon Comparison diagram of maximum sound pressure levels of Examples 2, 4 and 6 In the sound pressure waveform diagram of various sound sources, (a) is an impulse sound source according to the present invention, (b) is a cracker, (c) is a balloon Comparison of frequency characteristics of various sound sources Reverberation time measurement system configuration diagram The flowchart which shows the procedure of the reverberation time measuring method which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, the impulse sound source 1 according to the present invention includes a paper gun 2 made of rectangular paper and a grip 3 that detachably holds the end of the paper gun 2. The paper gun 2 has a single opening bag, and the two bags folded inside are opened with the fold 2b as an opening / closing axis to generate an impact sound. Consists of only. If there are two open bags, the time at which the two bags open slightly deviates and pulses are generated twice. To prevent this, one open bag was used. Moreover, if the structure of the paper gun 2 is used, the paper gun 2 can be repeatedly used as an impulse sound source if the paper gun 2 is folded each time it is used.

Since the paper gun 2 in this embodiment is not formed by joining the crease 2b only by folding the paper into a paper gun structure, the crease 2b of the paper gun 2 is firmly joined with tape or an adhesive so that there is no gap. I am letting. Moreover, in order to make the paper surface difficult to tear, it is reinforced with a resin film adhesive tape such as polypropylene. The paper gun 2 is firmly held by the grip 3 so as not to be detached from the grip 3 even if it is swung down, or is fixed to the grip 3 with two or more places with pins. If the paper gun 2 is damaged, it can be removed from the grip 3 and replaced with a new paper gun 2.

Note that it is possible to provide an impulse sound source with only the paper gun 2 without providing the grip 3. The material of the paper gun 2 is not limited to paper, but may be a composite material of paper and resin. If it is a synthetic material of paper and resin, it will be difficult to tear even without a reinforcing tape. If it is resin, it can be molded into the shape of the paper gun 2 from the beginning.

In addition, as shown in FIG. 2A, the impulse sound source 5 can be provided by providing the support member 4 along the inner side of the fold 2 b of the paper gun 2 without providing the grip 3. Reference numeral 6 denotes a gripping part for gripping in use. In addition, as shown in FIG. 2B, the support member 4 can be provided along the outside of the crease 2 b of the paper gun 2. The support member 4 has a rod shape and is formed slightly shorter than the length of the fold 2b, and can be made of a metal such as stainless steel or a hard resin.

  The support member 4 may be fixed to the paper gun 2 or may be detachably attached. When the holding part 6 is held by a finger of the hand, the support member 4 is also held at the same time. Thus, if the support member 4 is provided along the inner side or the outer side of the fold 2b of the paper gun 2, and the grip portion 6 is gripped with a finger and swung down, the impulse sound of the impulse waveform with reduced variation by the operator is obtained. Can be generated.

As shown in FIG. 3 and Table 1, six types (Examples 1 to 6) are prepared as paper guns 2 based on the paper size (three types) and the paper thickness (two types), and their characteristics are compared. Went.

  FIG. 4 shows the maximum sound pressure level according to the time weighting characteristic F for each 1/3 octave band when sounds generated from various sound sources are measured (five times). FIG. 4A shows the case of Example 1 (paper size: 1091 mm × 394 mm, paper thickness: 0.19 mm), and the reproducibility is particularly poor in a high sound range of 1000 Hz or higher. On the other hand, FIG. 4B shows the case of Example 2 (paper size: 1091 mm × 394 mm, paper thickness: 0.25 mm) with small variations in each time and reproducibility compared to Example 1. It turns out that is good. This is considered to be caused by the fact that the paper used for the paper gun 2 is thinner than the thin paper, and is easy to swing down without losing the resistance of air, and the swinging speed is stabilized. Particularly, when the size of the paper gun 2 is increased, air resistance is easily received.

Also, the cracker explosive sound shown in FIG. 4 (c) and the bursting sound of the balloon shown in FIG. 4 (d) both have large variations due to individual differences in the entire band, and the maximum sound pressure level is low in the low sound range. I understand.

FIG. 5 compares the difference in size of the paper gun 2 with respect to Example 2 (paper size: 1091 mm × 394 mm) and Example 4 having the same paper thickness (0.25 mm) and different paper sizes. (Actual size of paper: 854 mm × 302 mm) and Example 6 (paper size: 594 mm × 210 mm) are values obtained by arithmetically averaging the results of five measurements. According to this, the maximum sound pressure level tends to be higher when the size of the paper gun 2 is larger. When Example 2 and Example 4 are compared, there is no significant difference in the high sound range, but Example 2 shows a larger sound pressure level in the low sound range.

  The impulse response integration method needs to give sufficient consideration to the S / N ratio especially in the low sound range as compared with the noise intermittent method. Therefore, it is desirable that the sound source can secure a sufficient sound pressure level in the low sound range. Therefore, it is considered that Example 2 (paper size: 1091 mm × 394 mm, paper thickness: 0.25 mm) with a large paper thickness and a large paper gun 2 size is suitable under the conditions of the impulse sound source 1. It is done.

  FIG. 6A shows an example of the second embodiment, FIG. 6B shows an example of the sound pressure waveform of the cracker, and FIG. Example 2 shows an impulse sound pressure waveform having a sharp peak compared to a cracker or a balloon, and as shown in FIG. 7, it can be seen that it has a relatively flat frequency characteristic up to around 1000 Hz. The low frequency component is very important for reverberation time measurement. If the impulse sound source according to the present invention is used, it is possible to emit an impulse sound that sufficiently contains a low-frequency component as compared with a cracker or a balloon. As an impulse sound source for simply measuring the reverberation time in the field, it is considered to have sufficient sound output characteristics.

Next, a reverberation time measurement system 11 that implements the reverberation time measurement method according to the present invention includes an impulse sound source 1 and 5 composed of a paper gun 2 as a sound source and an impact generated by the impulse sound source 1 and 5 as shown in FIG. A microphone 12 for collecting sound, a sound level meter 13 for measuring an impulse response from an impact sound collected by the microphone 12, and a personal computer 14 for processing data output from the sound level meter 13 to calculate a reverberation time. The sound level meter 13 and the personal computer 14 may be integrated.

A reverberation time measuring method according to the present invention by the reverberation time measuring system 11 configured as described above will be described. In the reverberation time measuring method, as shown in FIG. 9, first, in step SP1, an impact sound is generated by the impulse sound sources 1 and 5 in the room to be measured (impulse sound generation step). Next, in step SP2, the impact sound generated in the impulse sound generation process is collected by the microphone 12, the impulse response is measured by the sound level meter 13, converted into data, and stored in the personal computer 14 (impulse response measurement process).

Next, in step SP3, the impulse sound generation step and the impulse response measurement step are repeated a predetermined number of times (for example, five times) (repetition step). Next, when it is determined in step SP3 that the process has been repeated five times, in step SP4, the reverberation time of the room is calculated by the personal computer 14 by the impulse response integration method from the impulse response measured in the repetition process (reverberation time calculation process).

By using the impulse sound sources 1 and 5, it is possible to generate an impulse sound having an impulse waveform with less tailing compared to a cracker or a balloon, so that the reverberation time measurement accuracy can be improved.

Advantageous Effects of Invention According to the present invention, it is possible to provide an impulse sound source that is inexpensive, easy to carry, can be repeatedly used, and can generate an impulse sound with a stable and good reproducibility. In addition, since a sound source that can generate an impact sound with an impulse waveform with less tailing is used, it is possible to provide a reverberation time measurement method that improves the reverberation time measurement accuracy.

DESCRIPTION OF SYMBOLS 1,5 ... Impulse sound source, 2 ... Paper gun, 2a ... Bag (sound-producing part), 2b ... Crease, 3 ... Grip, 4 ... Support member, 6 ... Holding part, 11 ... Reverberation time measurement system, 12 ... Microphone, 13 ... Sound level meter, 14 ... personal computer.

Claims (2)

An impulse sound source for measuring the reverberation time in a room , comprising a sound generating portion having a structure on one side of a paper gun, supporting a structure on one side of the paper gun and serving as a gripping portion on a fold serving as an opening / closing axis of the paper gun It provided a support member also functions detachably, by swinging down the sound generator, an impulse sound source, characterized in that to occur impact noise. A method for measuring reverberation time in a room, wherein an impulse sound is generated by an impulse sound source according to claim 1 and an impulse response is measured by the impulse sound generated in the impulse sound generation step. A measurement step, a repetition step of repeating the impulse sound generation step and the impulse response measurement step a predetermined number of times, and a reverberation time calculation step of calculating a reverberation time by an impulse response integration method from the impulse response measured in the repetition step. A characteristic reverberation time measurement method.