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The ANIR Corpus - Impulse Responses

   
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For all vehicles, impulse response are estimated for each loudspeaker and microphone combination. The acoustic paths considered here are the paths from the, e.g., headrest loudspeakers, mouth loudspeakers or standard loudspeakers to the standard microphones or the ear microphones. Consequently, all standard and ear microphone signals can be fully simulated for an arbitrary combination of system output and local speech sources.

The impulse responses are estimated using the Normalized Least-Mean-Squares (NLMS) algorithm in the time-domain. Specifically, a white noise excitation and a fixed stepsize are used. All impulse responses are available at a sample rate of 48 kHz.

 

System Delay

The system delay of our measuring equipment was determined and removed from the impulse responses. Consequently, the delay contained in the impulse responses only describes the analog/acoustic path from soundcard output to soundcard input. This allows simulating an arbitrary communication system, especially with respect to the delay of the simulated system.

 

Calibration and Equalization

The impulse responses are measured using calibrated microphones, see the background noise section for more information on the calibration. Hence, signals simulated using the impulse responses can be analyzed with respect to their sound pressure level at the microphones. Impulse responses involving a mouth loudspeaker are, additionally, scaled in such a way that a digital excitation power level of -26 dBov simulates an average sound pressure of -1.7 dBPa at the Mouth-Reference-Point (MRP). Mouth and ear equalization is included in the impulse responses. Since linear-phase filters are used for equaliztion, the (group) delay of the filters is removed from the impulse responses after equalization.

 

Analysis and Download

In below visualization of the impulse responses, the impulse responses are grouped by loudspeaker and microphone categories. The analyses provided show the impulse responses in the time domain, both an un-smoothed and a terz-smoothed version of the magnitude frequency responses, and the energy-decay curves. You can download the impulse responses individually on this page or all of them together as a zip file in the download section.