What is the reverberation room?
The reverberation room is a room for acoustic experiment used to evaluate the sound absorption coefficient and sound transmission loss of the acoustic material. It has reflective walls, floor, and ceiling, achieving an approximated diffused sound field in a limited space. The major purposes of reverberation rooms are following, but the reverberation room is used to evaluate the sound insulation performance of automobiles recently.
(1) Measurement of the sound absorption coefficient
(2) Measurement of the sound transmission loss
(For this purpose, either a coupled anechoic and reverberation rooms or two coupled reverberation rooms, which have an opening between the two rooms for setting up the test specimen is required.)
(3) Measurement of the sound power level
Nihon Onkyo Engineering can offer a comprehensive proposal from the design, construction of a reverberation room to the measurement system to be used with and training of the customer.
Reverberation room design
To determine the room volume and shape is the most important topic for designing a reverberation room. In general, a larger reverberation room is required to measure low-frequency characteristics. As for the shape of the room, irregular shaped rooms with slanted walls and ceiling for achieving diffuse sound field condition are common in Japan, but the cuboid reverberation rooms with an appropriate ratio of room dimension with some improvement have become more common. Nihon Onkyo Engineering has constructed a wide variety of reverberation rooms, from full-scale concrete reverberation rooms to paneled reverberation rooms that can be easily installed even in locations with load-bearing concerns. In addition to anechoic chambers required for measuring sound transmission loss, we are able to offer various projects according to various customer needs.
Acoustic performance evaluation of small samples such as automotive interior material
The current trend in the automotive industry is to use material with appropriate transmission loss and sound absorption coefficient properly in order to provide a comfortable and quiet cabin for customers. To evaluate small samples, using a small reverberation chamber is best and makes sense, but it has many technical difficulties to obtain stable measurement results. Nihon Onkyo Engineering has developed various ideas, devices, and techniques to improve the sound field that can be applied for small reverberation room measurement, thus ensuring evaluation of the acoustic performance of small samples is as precise as possible. Furthermore, we extensively examine our measurement systems and minimize instability of measurement results. We have many years of experience in setting up measurement systems for the sound absorption coefficient in reverberation room, moreover the sound transmission loss measurement systems measured with a coupled reverberation room and anechoic room.
Sound insulation performance evaluation of assembled components
Recently, in addition to material testing, sound insulation performance in cars is evaluated on components assembled from several parts, such as doors, floor panels, and dash panels. In such cases, a large-scale sound transmission loss suite, which means a coupled reverberation and anechoic rooms is required. As for measurement systems, Nihon Onkyo Engineering can propose various systems that include a microphone positioning system for automatic measurement of near-field sound intensity, noise source identification system Noise Vision, and other systems to meet customer needs.
Evaluating sound insulation performance of a vehicles
Another application using a reverberation room in the automobile industry is to evaluate the sound insulation performance of a vehicle. The sound pressure level distribution inside of the reverberation room is almost uniform. When a vehicle is placed in a reverberation room, the sound pressure level around the vehicle becomes nearly uniform, and vehicle's hot spot of sound insulation can be identified within a short period by measuring from inside of the vehicle. Using Noise Vision, our sound source identification and visualization system, is the most suitable choice for this kind of measurement.