Reference sound pressure level flowchart

[flipflop]

The TV SPL looks off. 20,000+ cu ft... what kind of use case is that for TV... that is a movie use case. Also note that TV shows use very high dynamic range compression. I turn the volume down 10-20 dB compared to movies.

Preferred Listening Levels and Acceptance Windows for Dialog Reproduction in the Domestic Environment found that 60 dBA is "a typical listening level for television viewing in actual homes".
I doubt that the TV shows, which brickwall their audio content, care about using the correct reference SPLs. The louder, the better.

 

[Senior NEET Engineer]

Preferred Listening Levels and Acceptance Windows for Dialog Reproduction in the Domestic Environment found that 60 dBA is "a typical listening level for television viewing in actual homes".
I doubt that the TV shows, which brickwall their audio content, care about using the correct reference SPLs. The louder, the better.

The movies tree root should point to "size of your room" node instead and TV tree root should be removed for now. Loudness is pretty consistent for TV... there should be a standard somewhere.

 

[flipflop]

TV tree root should be removed for now. Loudness is pretty consistent for TV... there should be a standard somewhere.

Are you saying that the cited source for TV reference levels is not a/the standard?

 

[Senior NEET Engineer]

Are you saying that the cited source for TV reference levels is not a/the standard?

SMPTE RP 200 is for movies.

 

[dasdoing]

I think this list is inspired by control room levels?
-20dB is good for mixeng because there should be headroom left for the mastering.
end users should use something like -3 to -6

 

[RayDunzl]

Preferred Listening Levels and Acceptance Windows for Dialog Reproduction in the Domestic Environment found that 60 dBA is "a typical listening level for television viewing in actual homes".

I'll buy that:

I doubt that the TV shows, which brickwall their audio content, care about using the correct reference SPLs. The louder, the better.

My experience:

My TV (optical output) is less loud overall than my HDRadio (optical output) or CD Player (optical output) or PC output (USB to optical)..

The program content is not smashed to the limits as is the current tendency for consumer music. If I switch to other sources, I usually have to turn it down a bit.

This is a cable signal, and it does have a low frequency cutoff on this program. Other content has greater range.

TV:

 

[dasdoing]

I think this list is inspired by control room levels?
-20dB is good for mixeng because there should be headroom left for the mastering.
end users should use something like -3 to -6

again,
http://www.voesd.at/files/Multichannel_Music_Mixing.pdf is for PRODUCTION, not for playback of the mastered endproduct. imo the guide should be corrected. the masters don't have -20dB loudness

 

[flipflop]

again,
http://www.voesd.at/files/Multichannel_Music_Mixing.pdf is for PRODUCTION, not for playback of the mastered endproduct. imo the guide should be corrected. the masters don't have -20dB loudness

I wouldn't mind updating it, but you have to cite a credible source which shares the view that consumer playback SPLs should be different from the ones used in mixing and mastering rooms.

 

[dasdoing]

I wouldn't mind updating it, but you have to cite a credible source which shares the view that consumer playback SPLs should be different from the ones used in mixing and mastering rooms.

I wont say that I am right.
it's just how I understand it:
-20dB in production is there in order to leave headroom for mastering. In the mastering stage the loudness will be brought up with compression and limiting.
Do we have any sound engenieers here that could clear this up?

 

[Pluto]

Don't confuse headroom on recording media with listening level. I don't have the time to look at all the references but I believe the -20dB figure refers to the advised headroom for the very loudest material against the absolute peak capability of the recording media. The last thing you want on a live recording is to go over absolute maximum level, so a safety margin of 20dB is often advised. If that master recording is to find its way onto a loudness-war contestant, the very highest peaks on the original (say -18dB reference max.) may well end up at -0.2dB on the end product.

That's mastering for you.

 

[tomelex]

I believe this is why so many audiophiles listen at levels that are louder than reality - especially for small ensemble acoustic music. The louder level is like boosting the bass & treble. Which is ironic, since many of these same audiophiles eschew the use of tone controls, not realizing their volume knob is a kind of tone control.

yes, the so called hi-end in the seventies did away with tone controls, even though on all the better preamps of the time there was a bypass switch, the reason they did away with tone controls has a lot to do with their inability to design them in the small cottage industry shops so they just said they were bad and got in the way, when in reality there is one general volume control setting you need to be at to try to duplicate somewhat wha tthe recording engineer was aiming at for balance across the band,.....and we all do not always listen at high volumes for sure, and some speakers are bass heavy to start with so as you turn it up things get skewed and you need to turn to those "missing" tone controls to set things back to a listening experience that makes more sense for you as an individual.

 

[BDWoody]

and we all do not always listen at high volumes for sure, and some speakers are bass heavy to start with so as you turn it up things get skewed and you need to turn to those "missing" tone controls to set things back to a listening experience that makes more sense for you as an individual.

I have an old Nakamichi preamp with a contour knob...the suggestion is to set the main volume knob at the loudest listening you'll do, then adjust interim levels with the contour control...have to say, it works great. Wish more newer units had such a thing...

 

[MRC01]

yes, the so called hi-end in the seventies did away with tone controls ...

I remember that and am glad to see tone controls (or EQ more generally) making a comeback. Especially in this age of DSP effectively eliminating side effects when used judiciously. My current DAC/Preamp has tone controls, good old fashioned knobs you physically turn. They're implemented in DSP but I still enjoy the nostalgia every time I use them, or even look at them. They come in handy because the sad fact is that there will always be some great music with not-so-great sounding recordings.

Of course tone controls can't fix every flaw, far from it. But they do help with the most common recording flaws which are related to tonal balance.

 

[dasdoing]

Don't confuse headroom on recording media with listening level. I don't have the time to look at all the references but I believe the -20dB figure refers to the advised headroom for the very loudest material against the absolute peak capability of the recording media. The last thing you want on a live recording is to go over absolute maximum level, so a safety margin of 20dB is often advised. If that master recording is to find its way onto a loudness-war contestant, the very highest peaks on the original (say -18dB reference max.) may well end up at -0.2dB on the end product.

That's mastering for you.

when you master to up to -0.2dB, is your system calibrated with -20dB pink noise to 83dB?
in the other topic you said engineers master at a variety of listening levels; that would make calibrating home listening nonesene from the start as you never know at which levels stuff was mastered.

 

[Pluto]

when you master to up to -0.2dB, is your system calibrated with -20dB pink noise to 83dB?

No.

Not that I would ever run up to that level. Not even close.

in the other topic you said engineers master at a variety of listening levels; that would make calibrating home listening nonsense from the start

Yup!

 

[JIW]

Why use a reference SPL?
"The reference listening level is defined as a preferred listening level, produced with a given measuring signal at the reference listening point. It characterizes the acoustic gain of the reproduction channel in order to ensure the same sound pressure level in different listening rooms for the same excerpt."
"Reference level is a calibrated volume setting used for both movie production (in dubbing stages and post production houses) and reproduction (in screening rooms and theaters). The human hearing system is non-linear, especially in the bass, so having a consistent playback level – a reference – is critical if the mix is to translate from one production house to another and audiences are to hear the director’s intent in terms of the balance in the soundtrack between dialog, effects and ambiance."

Calibrating loudspeakers
1. Copy the first test tone, 1 kHz sine wave at -20 dBFS, to a digital audio workstation, and then copy it into each of the channels to be employed.
2. Play the file, setting the output level controls of the workstation to unity gain, the console input to unity gain, and the console master level control to unity gain. You may keep the monitor level control low for the time being.
3. Set the level of each channel in turn for the sine-wave test level for the meter in use, such as -20 dBFS for digital meters, or 0 VU for VU meters.
4. Copy the second test tone, band-limited pink noise at -20 dBFS, to each channel of the digital audio workstation.
5. Play one channel at a time if calibrating for music or television. Play all channels except the subwoofer (which is calibrated separately) if calibrating for movies.
6. Put a sound level meter at the position of the center of the head of the normal position for the operator, pointing it at the loudspeaker channel in use. Keep your body perpendicular to the meter, off to one side, as the level can be affected by a strong reflection off your body.
7. Set the individual channel level controls, such as power amplifier gain controls, or gain controls on powered loudspeakers for the Sound Pressure Level measured C-weighted and slow.

Or put more simply, using playback for movies as an example:
"Reference level for all channels except low frequency effects is calibrated by adjusting the audio chain such that a pink noise signal recorded at -20dB relative to full scale (0dB) creates 85dB sound pressure level as measured with a C weighted SPL meter at the seating locations."

Flowchart
View attachment 48404
*This is 80 dB @ 1 kHz if the headphones follow the Harman target curve.

Sources
[1] Dolby 5.1-Channel Music Production Guidelines
http://www.voesd.at/files/Multichannel_Music_Mixing.pdf

[2] Methods for the subjective assessment of small impairments in audio systems
Recommendation ITU-R BS.1116-3 (02/2015)
https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1116-3-201502-I!!PDF-E.pdf

[3] A Statistical Model that Predicts Listeners’ Preference Ratings of Around-Ear and On-Ear Headphones
http://www.aes.org/e-lib/browse.cfm?elib=19436

[4] A Statistical Model That Predicts Listeners’ Preference Ratings of In-Ear Headphones: Part 1 – Listening Test Results and Acoustic Measurements
http://www.aes.org/e-lib/online/browse.cfm?elib=19237

[5] RP 200:2012 - SMPTE Recommended Practice - Relative and Absolute Sound Pressure Levels for Motion-Picture Multichannel Sound Systems — Applicable for Analog Photographic Film Audio, Digital Photographic Film Audio and D-Cinema
https://ieeexplore.ieee.org/document/7289847

[6] ATSC Recommended Practice: Techniques for Establishing and Maintaining Audio Loudness for Digital Television (A/85:2013)
https://www.atsc.org/wp-content/upl...tablishing-and-maintaining-audio-loudness.pdf

Where in [3] and [4] do you find reference levels? I don't have access to those papers but it seems odd for listener preference research papers to make such prescriptions.

I have access to a paper also by Olive and Welti but with E. McMullin instead of Khonsaripour: Listener preference for different headphone target response curves. There they say average levels were 78 dB B-weighted.

The average playback level of the music was adjusted to a comfortable level of 78 dB (B-weighting).

Also, [2] while not giving exact levels says that the reference level of headphones should be set such that its loudness matches that of the speakers.

8.4.2 Headphone reproduction
The level should be adjusted in such a way that a loudness equal to the reference sound field produced by loudspeakers is achieved. To determine equal loudness the subject should be positioned at the reference listening point.

Further, [2] uses -18 dBFS pink noise instead of -20 dBFS so your reference level should be 2 dB lower, i.e. 76 dBA.

 

[flipflop]

Where in [3] and [4] do you find reference levels? I don't have access to those papers but it seems odd for listener preference research papers to make such prescriptions.

[3]:

2.7 Relative and Absolute Playback Levels
The relative levels of the virtual headphones were matched according to ITU-R BS 1770-4 loudness model [18]. The authors then performed fine-tuning of the level adjustments through informal listening. The absolute playback level was then set to produce an average level of 85 dB (slow, C-weighted), equivalent diffuse field level.

[4]:

2.7 Relative and Absolute Playback Levels
The relative levels of the virtual headphones were matched according to ITU-R BS 1770-4 loudness model [18]. The authors then verified the relative loudness through informal listening. The absolute equivalent diffuse field level was 82 dB (slow, C-weighted) averaged over the duration of the sound loop.

I have access to a paper also by Olive and Welti but with E. McMullin instead of Khonsaripour: Listener preference for different headphone target response curves. There they say average levels were 78 dB B-weighted.

That paper is from 2013 and compares different target curves. The paper I've cited is from 2018 and uses the de facto standard Harman target curve.

Further, [2] uses -18 dBFS pink noise instead of -20 dBFS so your reference level should be 2 dB lower, i.e. 76 dBA.

The standard states 78 ± 0.25 dBA at -18 dBFS:

 

[JIW]

[3]:

[4]:



That paper is from 2013 and compares different target curves. The paper I've cited is from 2018 and uses the de facto standard Harman target curve.


The standard states 78 ± 0.25 dBA at -18 dBFS:
View attachment 413731

Thanks for the quotes from [3] and [4]. What makes the average levels used in the research prescriptive as reference levels?

You write in your original post:

4. Copy the second test tone, band-limited pink noise at -20 dBFS, to each channel of the digital audio workstation.

 

[flipflop]

What makes the average levels used in the research prescriptive as reference levels?

The fact that those levels are used by the most prominent researchers in the most recent research. Until we've got actual standards for headphones, I believe those are the best reference levels to go by.

You write in your original post:

I suppose I should've made it clearer that it only applies to calibrating speakers for movies and not music.

 

[JIW]

The fact that those levels are used by the most prominent researchers in the most recent research. Until we've got actual standards for headphones, I believe those are the best reference levels to go by.

I suppose I should've made it clearer that it only applies to calibrating speakers for movies and not music.

Those are average levels for music. How do they relate to the reference signal of -20 dBFS pink noise?

There are standards for headphones as I pointed out but they are not stated as SPL for a specific input but instead equal loudness to speakers at their reference level (ITU-R BS1116-3 8.4.2). The same is required by EBU Tech 3276 2.5:

No satisfactory method for measuring sound pressure levels produced by headphones can be recommended. The level should be adjusted in such a way that a perceived loudness equal to a reference sound field produced by loudspeakers is achieved.