[ProAudio] Calibrated playback level
dlj at josephson.com
Tue Sep 28 12:35:22 PDT 2021
As many of you know I have been teaching a few people in the aircraft business about sound and noise and perception, trying to bring in best current practice from psychoacoustics, theater sound and acoustic metrology. They are beginning to get it, and there’s work going on across a bunch of groups focusing on accurate playback of ambient recordings and layering new aircraft sounds into those ambients as if the plane had been flying through them.
Progress report on the planes … some of them are very quiet. There’s a video of the Joby S4 and some conventional aircraft at https://www.youtube.com/watch?v=itP8-3j2UZI … this is an accurate binaural recording made with a setup I provided. You can see lots about the aircraft on the web, it carries a pilot and four passengers. Takeoff/departure maximum is about 65 dB(A) at 300 feet, with almost no tonal or impulsive content, compared to about 30 dB higher for a helicopter of similar capacity. Overflight at 1500 feet is about 20 dB lower; there are six very efficient slow-turning propellers. At the moment the cooling fans inside the motors are louder than the props themselves, but these are being fixed in a coming revision.
We (and NASA, and some others) are making libraries of ambient soundscape recordings to demonstrate what these things sound like in different neighborhoods. Each ambient includes a 94 dB SPL 1 kHz tone, which gets replaced with 500-2000 Hz filtered pink noise of the same rms level. That’s scaled to play back in the listening space at 94 dB, all speakers operating.
Is there a simpler way to do this? Any other best-practices for metadata and archiving of ambient sound recordings for consistently accurate playback level would help.
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