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Impulse response measurement system

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AEIRM impulse response measurement system

Photo of AEIRM impulse response measurement system

AEIRM is an impulse response measurement system used on a PC.
Impulse response is widely used for research, development, and measurement in acoustics with results that can be used as not only basic analysis and simulation data but also in an endless number of other applications. Using a high-performance audio interface, AEIRM systems have full synchronization for signal recording and playback. In addition, an extra analyzer is no longer required when using the system, making this system both incredibly compact and portable.

AEIRM characteristics

AEIRM system configuration
  • Sampling frequency: 96 kHz, Resolution: 24 bit (on Windows; depends on audio interface)
  • Measurements using M-sequence (Maximum Length Sequence, quasi-random signal) and TSP (Time Stretched Pulse, swept sine signal)
  • Digital audio input/output (TOSLINK, AES/EBU)
  • FFT analysis and frequency characteristic (frequency response characteristics) calculation
  • Multi-channel measurement for efficient, simultaneous multi-point measurement
  • Inverse filter calculation for room acoustic, acoustic signal processing, and noise control, and convolution processing with optional software
  • Audible system with convolution processing for laboratory reproduction of measured sound field
  • Special specifications that support microphone traverse system and moving sound sources are available
  • Similar hardware configuration for construction of various applications using high-quality audio interfaces

Case study: Audible differences in acoustic characteristics of building interior material

Nihon Onkyo Engineering has conducted trial listening evaluations comparing different materials based on impulse responses of measured reflected sounds for various interior material used in recording studios and other locations by installing the material in an anechoic room. We use auralization technology to reproduce the subtle nuances of sound quality between wall surface materials in an approach that is highly appreciated by customers. Using impulse responses allows us to separate and handle direct and reflected sounds individually, facilitating processing through the ability to extract only reflected sounds and slightly change the frequency or other characteristics.

Case study: Identification of and countermeasures against causes of unwanted reflection

Sound pressure levels may increases at unexpected points when measuring road traffic or railway noise due to various kinds of reflected sounds. This phenomenon appears when there is an elevated highway over a road, railway track, or tall buildings in the neighborhood. By setting the speaker as the sound source position and measuring the impulse response at the sound-reception point, Nihon Onkyo Engineering is able to verify how much direct sound and reflected sound influence the overall sound pressure levels. Moreover, using an application that analyzes the arrival direction of reflected sound makes it possible to obtain more detailed analysis, such as identifying those buildings causing significant reflections.

Analysis of variation between measuring instruments

Nihon Onkyo Engineering has various kinds of measuring equipment--including sound level meters--and performance of all equipment is regulated according to JIS standards with performance maintained through periodic testing. Furthermore, in an effort to provide more reliable measurement, our inspections are performed using reliable impulse responses with high measurement reliability for changes of frequency characteristics when setting the windscreen and for sound pressure level variations among sound level meters.

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