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Safe listening levels and headphone voltage/power requirements

Robbo99999

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Yeah, it might be one of the reasons why Harman found the preferred bass for in-ears to be higher than for headphones, because the stapedius reflex mostly reduces transmission at lower frequencies, so listeners may have compensated for this by turning up the bass control. The paper linked above does also say though:

(Maybe this is a contributor to the flattening of the equal loudness contours in the midrange with increasing SPL?)

Also of note is the prevalence of the reflex was actually found to only be ~75% in this study, but more common at ~85% for younger listeners ages 18-30. This may (partly) explain the variation in preferred bass Harman found with in-ears:

View attachment 235368

And also the higher preferred bass by younger listeners in their over-ear tests (which may still have triggered the stapedius reflex for some, as people's trigger SPL threshold ranges from ~70-100 dB, and Harman's listening level is within this range):

index.php


Interestingly, the paper @xnor linked also mentions infrasound (which I've previously posited could be contributing to perceptions of bass impact):

This boosted infrasound would more readily trigger the stapedius reflex. Initially you'd think this would mean less perceived bass impact, but it might be more complicated than that. The reflex has a letency of ~10 milliseconds, but maximum tension of the intra-aural muscles involved may not be reached for 100 milliseconds or more, too late for sudden, intense sounds (e.g. percussive sounds like a kick-drum). Also, this tension reduces by about 50% after a few seconds. This could result in repeated initiation of the stapedius reflex when listening to music, with the sound during periods after sudden loud (e.g. percussive) parts sounding quieter, but not those sudden loud parts themselves, due to the latency of the reflex, and its relaxation. This could then be an explanation for an increased perception of percussive bass impact, and could even explain @Resolve 's (and others') perception that some headphones (which it seems mostly have well-sealed front volumes) have greater 'macrocontrast/macrodynamics' than others with a similar response above 20 Hz - because the stapedius reflex literally changes the dynamic range of the ear:

Unless sub-20 Hz responses of such headphones are measured, we won't be able to investigate this potential influence of infrasound and static pressure on perceived sound further.
Doesn't really sound healthy having the stapedius reflex initiated with each drum strike, lol! [shrug] You'd think that if it was being repeatedly initiated then it would also cause constant fluctuations in tonality, like warbling or something, lol!
 

GaryH

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I think it's this one: https://www.aes.org/e-lib/browse.cfm?elib=15786

Abstract:

(emphasis by me)

Basically, the tighter the seal and the smaller the enclosed volume of air the stronger this effect gets. Worst case is probably deep-insertion in-ears that completely seal the ear canal.
Thanks. Sounds terrifying! But note this is a paper that's the basis for a commercial product i.e. the ADEL module by Asius Technologies, so they may be overstating the case. Most modern IEMs feature a front volume vent, which does exactly the same job as the (expensively licensed) ADEL module:
https://www.reddit.com/r/headphones/comments/8axyhy/_/dx2exhm So like a lot of these things, it's a solution without a problem (or rather in this case a problem with a solution that already exists, for much less cost).
 

GaryH

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Doesn't really sound healthy having the stapedius reflex initiated with each drum strike, lol! [shrug] You'd think that if it was being repeatedly initiated then it would also cause constant fluctuations in tonality, like warbling or something, lol!
Haha maybe the brain compensates for any potential change in tonality.
 
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xnor

xnor

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Unless sub-20 Hz responses of such headphones are measured, we won't be able to investigate any of this further.
Generally speaking, if the FR is "flat" down to 20 Hz then it's not unreasonable to assume that the headphone will continue to produce significant SPL at 10 Hz.

This "pressure chamber" effect is also well known in the speaker world in room acoustics and especially car hifi: at some point sound waves become static pressure differences in the room. Open a window or break the headphone-ear seal and SPL will drop significantly because the pressure cannot be maintained.

Explains why I always preferred headphones without tight seal, hate completely sealing in-ears, and am using highpass filters when using headphones/in-ears that have a tighter seal.
 

MRC01

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...
Conclusions
85 dBA should not be considered a universally safe limit, especially not for children, people with sensitive hearing, when regularly listening for several hours, or when being exposed to other potentially louder noise sources throughout the day.
Therefore, I recommend to stay below 85 dBA when listening to music.
...
I agree and keep average levels below 80 dB myself. Most of my listening is to uncompressed high dynamic range music, so even with average levels below 70 dB, occasional peaks hit 90 (not sustained). But for most modern music, which is heavily compressed having little or no dynamic range, staying below 85 dB (better yet, 80 dB) is a wise choice.

Now consider the levels at which we measure equipment. 50 mV is often said to be for IEMs. Yet that has always seemed misleading to me. Even the venerable HD-580/600 with its low voltage sensitivity is around 79-80 dB at 50 mV.
 

GaryH

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Generally speaking, if the FR is "flat" down to 20 Hz then it's not unreasonable to assume that the headphone will continue to produce significant SPL at 10 Hz.
Not necessarily, anyway we need to go below 10 Hz to ~0 Hz to characterize actual static pressure (and so degree of front volume seal).
Explains why I always preferred headphones without tight seal, hate completely sealing in-ears, and am using highpass filters when using headphones/in-ears that have a tighter seal.
Yeah if it really bothers you and you're ok missing out on the visceral, tactile impact infrasonics can bring, just add in a high-pass filter around 20 Hz to an EQ when using high-sealing headphones/IEMs, that's an even cheaper solution than a front vent :) So it really isn't a problem.
 
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xnor

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I agree and keep average levels below 80 dB myself. Most of my listening is to uncompressed high dynamic range music, so even with average levels below 70 dB, occasional peaks hit 90 (not sustained). But for most modern music, which is heavily compressed having little or no dynamic range, staying below 85 dB (better yet, 80 dB) is a wise choice.
Yeah, I've set the target level to 80 with v3 of the spreadsheet. People are free to adjust the target but I'm recommending here and in the notes in the spreadsheet to keep it below 85.

Now consider the levels at which we measure equipment. 50 mV is often said to be for IEMs. Yet that has always seemed misleading to me. Even the venerable HD-580/600 with its low voltage sensitivity is around 79-80 dB at 50 mV.
My modern pop/rock sample has a total weighted RMS amplitude 12 dB lower than that of a sine wave so a 125 dB SPL/Vrms in-ear will produce an equivalent of 87 dBA with just 50 mV (peaks over 50ms windows are 9 dB higher).
It's easy to see how people ruin their hearing. Even the crappiest headphone outputs can usually output hundreds of mV. Dongles for less than $10 can produce north of 110 dBA with such in-ears.

HD600 is roughly 20 dB lower though ... but also has 10x the impedance so it's a far easier load which means crappy headphone outputs will output higher voltages as well.
 

MRC01

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My modern pop/rock sample has a total weighted RMS amplitude 12 dB lower than that of a sine wave so a 125 dB SPL/Vrms in-ear will produce an equivalent of 87 dBA with just 50 mV (peaks over 50ms windows are 9 dB higher).
...
HD600 is roughly 20 dB lower though ...
Perhaps, yet I was making a simpler point. Play a waveform having a voltage amplitude of 50 mV into the HD-580/600 and it produces an SPL of 79-80 dB. That's not "quiet", which means the 50 mV test/measurement is not just for IEMs, but also relevant to full size headphones.
 
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xnor

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@xnor What are the LUFS values in the Music paramter box in the spreadsheet?
The BS-1770 loudness of the entire track.

In foobar2000 you can do RG - scan track and the result will be relative to -18 LUFS. So if it said "Track Gain: +1 dB" that would mean the track is 1 LU too soft, so the track loudness is -19 LUFS. (I tried to explain that in #18.)

There are many other ways to analyze your own files. If you have a DAW you may use a monitoring plugin like TBProAudio's dpMeter. That also allows you to calculate total RMS amplitude A-weighted.

Finally, if you have the numbers for a set of files that you think are useful for other people as well then please share them and I will add them to the spreadsheet.
 

Soundescape

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Yes I understand this, what I meant is that how this is going to interact with the main LUFS target in the spreadsheet.
E.g. I measure an already LUFS normalized track (or track in the album context) with streaming services.
 
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xnor

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If you set the target to -10 and the music has a loudness of -6 then this will add another 4 dB to the total attenuation.... because the track is too loud by 4 dB.

If the music had a loudness of -16 then it would need to be boosted by 6 dB. This will turn the "loudness limit" cell red, see the note in the spreadsheet:
If >0 then loudness normalization would require a boost. We assume any boost would result in clipping and is therefore not applied.

This means this type of music will be played at lower loudness (lower by this value) and volume needs to be adjusted by hand.

Try to lower the loudness target, switch to music with higher loudness or reduce the dynamic range (changing the RMS and loudness values) by adding a compressor.

Basically, loudness normalization is assumed to only attenuate by the difference between the target and loudness of the track/music.

If the track/music is too quiet and below the target then this effectively disables loudness normalization. In that case you're back to adjusting the volume manually by hand.
This is also reflected by the higher volume setting in the "classical" column if the target is set too high.

If you don't listen to classical then you probably don't need to worry, although I would be interested to see RMS/loudness values for other music "profiles" or genres to see if they're closer to the classical or modern pop/rock recordings.
 
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Soundescape

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If you set the target to -10 and the music has a loudness of -6 then this will add another 4 dB to the total attenuation.... because the track is too loud by 4 dB.
Don't we care only that we have a target of -10 LUFS?
 
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xnor

xnor

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Is this expressed by the LUFS cell in the music parameters?
Indirectly.

As explained in my long and possibly confusing posts, the "Target Level" is based on dB SPL A-weighted (short: dBA) since that is based on an absolute reference and an established reference for hearing loss.
In the music parameters, the "Total RMS weighted" uses the same weighting as the target level.

P/V/I requirements are based on these two numbers and the sensitivity of the headphone.


BS-1770 loudness target and loudness parameters were added later on. Loudness is specified as LUFS, so relative to full-scale. It tells you how loud a track will be perceived relative to a ~1 kHz full-scale sine wave. LUFS cannot be directly translated into dB SPL.

The attenuation parameters as well as loudness normalization (which is basically just another source of attenuation) are used for the Gain/Volume calculations.
 

Soundescape

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Ok so we suppose that Rock/POP type tracks have a expected pre-normalizalizzation at -8 LUFS (on avg).

Then we just transform the LUFS difference with the target as a DB attenuation that we need to recover with the "volume knob".
 
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xnor

xnor

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Exactly. Since we know the voltage required and the max output of the amp we can calculate the volume setting.
However, if the signal is attenuated in any way (such as by loudness normalization) then we need to compensate that by increasing the volume.

And that's exactly what the spreadsheet shows. As you lower the loudness target, the volume setting will increase by the same amount such that you're always right on the main target level.
 
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