From dlj at josephson.com Tue Sep 28 12:35:22 2021 From: dlj at josephson.com (David Josephson) Date: Tue, 28 Sep 2021 12:35:22 -0700 Subject: [ProAudio] Calibrated playback level Message-ID: Greetings ProAudio, 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. Thanks David Josephson From kludge at panix.com Tue Sep 28 12:39:36 2021 From: kludge at panix.com (Scott Dorsey) Date: Tue, 28 Sep 2021 15:39:36 -0400 Subject: [ProAudio] Calibrated playback level In-Reply-To: References: Message-ID: <61536f78.B2gJMiHahODMFKGr%kludge@panix.com> I am merely reminded of Gabe Weiner's CDs which have a mention in the liner notes of what the sound pressure level of the first bar should be on playback. It is more explicit than "This album was mixed to be played loud so turn it up." --scott From lists at richardhess.com Tue Sep 28 13:15:38 2021 From: lists at richardhess.com (Richard L. Hess) Date: Tue, 28 Sep 2021 16:15:38 -0400 Subject: [ProAudio] Calibrated playback level In-Reply-To: References: Message-ID: <35e12d10-f05a-2806-c9c3-a2be5273981f@richardhess.com> Hi, David, It comes as no surprise that you and the other scientists have included the calibration tone in the recording. Honestly, considering that big round thing under my right hand, I don't think that there is any other way. While many professional reproducing systems (both studio and theatre) are calibrated for -X dBFS = Y dB SPL. There are still "volume controls" that can throw that off. One thing that I would assume is that the instructions should call for measuring it with the meter at "C" or "Flat" weighting, as "A" weighting might cause an inaccuracy. (I didn't look at the curve, but my recollection is there is a peak around 3 kHz). I suspect that the $100-300 SPL meters will be close enough for casual listening tests, but for serious testing a better meter and microphone would provide more accuracy. I wonder how different playback spaces might affect the perception of the noise, even if well-calibrated. Say for example, longer reverb times and many hard reflective surfaces vs. the proverbial "pillow factory*" The work you report on is exciting and thank you for sharing. Have you heard anything about the outcome of the attempts two decades or more ago to try and use community-level active noise cancellation around Burbank Airport? I recall it being announced, and I recall being very, very skeptical of its probability for success. Cheers, Richard * I must credit "pillow factory" to Dr. Gerre Hancock, the organist and master of choristers at St. Thomas Church in NY City where I recorded many things (and also attended as a parishioner). In the latter half of the 1970s, I was working at the ABC Television Network former facility on W66th Street in NY. One Christmas, the Choir of Men and Boys was invited to be on Good Morning America and later Gerre asked me, "Richard, why do you make all those studios to be like pillow factories?" Of course, the choir was used to singing in St. Thomas Church which had a reverb time of around five seconds, and the choral music did not sound as good in the studio...and I think the choristers may have even had problems hearing each other. On 2021-09-28 3:35 p.m., David Josephson via ProAudio wrote: > Greetings ProAudio, > > 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. > > Thanks > > David Josephson > _______________________________________________ > ProAudio mailing list > ProAudio at bach.pgm.com > http://bach.pgm.com/mailman/listinfo/proaudio -- Richard L. Hess email: richard at richardhess.com Aurora, Ontario, Canada http://www.richardhess.com/ http://www.richardhess.com/tape/contact.htm Quality tape transfers -- even from hard-to-play tapes. -------------- next part -------------- An HTML attachment was scrubbed... URL: From loujudson at mac.com Tue Sep 28 14:09:40 2021 From: loujudson at mac.com (Louis Judson) Date: Tue, 28 Sep 2021 14:09:40 -0700 Subject: [ProAudio] Pillow vs live - Re: Calibrated playback level In-Reply-To: <35e12d10-f05a-2806-c9c3-a2be5273981f@richardhess.com> References: <35e12d10-f05a-2806-c9c3-a2be5273981f@richardhess.com> Message-ID: <64A7DE57-54E8-408F-A387-E471D0BF1D3D@mac.com> Nice little story, Richard. Years ago I worked with the vocal group Kitka and the were asked to do a television performance to promote a local concert. They had the insight to ask me to bring in my mics and sound system to put reverb into the studio - no voice amplification, just reverb like their concerts. I used a catherdral settingg, and it was stunningly fine - and I gave a feed to the control room just in case they?d know what to do with it. I never heard the broadcast, but the smiles of the singers told me all I needed to know. Lou Judson * Intuitive Audio 415-271-8070 mobile I'm just a simple sound engineer, nothing more, nothing less. -- paraphrase of the Dalai Lama. > On Sep 28, 2021, at 1:15 PM, Richard L. Hess via ProAudio wrote: > > * I must credit "pillow factory" to Dr. Gerre Hancock, the organist and master of choristers at St. Thomas Church in NY City where I recorded many things (and also attended as a parishioner). In the latter half of the 1970s, I was working at the ABC Television Network former facility on W66th Street in NY. One Christmas, the Choir of Men and Boys was invited to be on Good Morning America and later Gerre asked me, "Richard, why do you make all those studios to be like pillow factories?" Of course, the choir was used to singing in St. Thomas Church which had a reverb time of around five seconds, and the choral music did not sound as good in the studio...and I think the choristers may have even had problems hearing each other. > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From 6807.chris at pop.powweb.com Tue Sep 28 19:00:03 2021 From: 6807.chris at pop.powweb.com (Chris Caudle) Date: Tue, 28 Sep 2021 21:00:03 -0500 Subject: [ProAudio] Calibrated playback level In-Reply-To: References: Message-ID: On Tue, September 28, 2021 2:35 pm, David Josephson via ProAudio wrote: > 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. Does that mean you have a calibrated acoustic source which generates a 94dB 1kHz acoustic tone, so that the level makes it all the way through the recording chain? Are you using omni mics, and that is something like the piston calibrators used to calibrate measurement mics? -- Chris Caudle From dlj at josephson.com Tue Sep 28 21:29:29 2021 From: dlj at josephson.com (David Josephson) Date: Tue, 28 Sep 2021 21:29:29 -0700 Subject: [ProAudio] Calibrated playback level In-Reply-To: References: Message-ID: <499E6242-0D81-4731-A068-071D25B1B131@josephson.com> Yes to all of that. The mics are in fact measurement omni mic capsules (Gefell MK221 on our C617 bodies) that are rated for use with standard pistonphones or active calibrators like the B&K 4231. David > On Sep 28, 2021, at 7:00 PM, Chris Caudle via ProAudio wrote: > > On Tue, September 28, 2021 2:35 pm, David Josephson via ProAudio wrote: >> 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. > > Does that mean you have a calibrated acoustic source which generates a > 94dB 1kHz acoustic tone, so that the level makes it all the way through > the recording chain? > Are you using omni mics, and that is something like the piston calibrators > used to calibrate measurement mics? > > -- > Chris Caudle > > > > > _______________________________________________ > ProAudio mailing list > ProAudio at bach.pgm.com > http://bach.pgm.com/mailman/listinfo/proaudio From dan at dandugan.com Tue Sep 28 22:00:27 2021 From: dan at dandugan.com (Dan Dugan) Date: Tue, 28 Sep 2021 22:00:27 -0700 Subject: [ProAudio] Calibrated playback level In-Reply-To: References: Message-ID: David Josephson, you wrote, > 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. For many years I?ve tried to calibrate my nature recording channels to 0dBFS = 70dBA SPL. That will handle 99.99% of environmental sounds. Exceptions have been thunder, Pacific chorus frogs nearby, and Osprey tilt-rotor aircraft. I do the channel calibration in a diffuse field (10 speakers) at 64dBA = -6dBFS, pink noise filtered 200-2000Hz, windscreens on. For species reporting study, and for aesthetic enjoyment, I monitor in the field and listen in the studio a lot louder than the natural level. This is for the same reason that birders look at birds through at least 8x (like 18dB?) binoculars. To extend the senses into the distance, to discern detail the naked eye/ear cannot. I want to develop a field calibrator for use with mic arrays with windscreens in place. Imagine a smartphone holder with a 1/2-meter telescoping probe that is touched to the outside of the windscreen assembly. The operator selects a pre-set channel, mic type, and angle of approach (think about a single windscreen containing M/S or ambisonic elements). The calibrator speaks the name of the channel and the angle, sends it in modem tones, and plays a burst of band-limited noise. Using a smartphone, the test noise is mainly high-frequency but that?s good, because at lower frequencies reflections from the operator?s body are significant?like 1.5 dB at 1K. -Dan