Sign in   |  Join   |  Help

A good tutorial on audio levels

rated by 0 users
Not Answered This post has 0 verified answers | 3 Replies | 0 Followers

Geoff Martin
Top 150 Contributor
Struer, Denmark
618 Posts
OFFLINE
Bronze Member
Geoff Martin posted on Wed, Jan 27 2021 8:10 AM

https://netflixtechblog.com/optimizing-the-aural-experience-on-android-devices-with-xhe-aac-c27714292a33

Yes, it's an advertisement for Netflix, but it's a good tutorial on the problem associated with audio levels and dynamic range across different formats.

cheers
- geoff

All Replies

Beobuddy
Top 25 Contributor
Utrecht, The Netherlands
3,843 Posts
OFFLINE
Founder

Thank you Geoff for the interesting article.

 

I have always assumed that the loudness function was designed for compensating the human hearing at lower levels. The human ear would be less sensitive for lower and higher frequencies at low level. Therefore a well designed loudness circuit (as was with B&O's version) gained only the bass and treble section at lower volumes and the gaining decreased when the volume was turned up.

You could check that when you pushed the loudness button on and off when your volume was more turned up. At about 3/4 off the maximum volume you shouldn't hear any difference, as if I remember that some (japanese)brands would still gain these bands rather noticable.

This doesn't match what I read in the article, where gaining is done over the complete frequency range at lower levels. Or did I miss something?

Geoff Martin
Top 150 Contributor
Struer, Denmark
618 Posts
OFFLINE
Bronze Member

The problem is that there are two definitions of "loudness".

One is the one you're talking about - a bass (and possibly treble) boost to compensate for the equal loudness contours (a.k.a. Fletcher Munson curves).

The other is the definition that psychoacoustics people use - which is a perceptual measure of how loud things sound. Measuring sound pressure level (SPL) does not always correlate with how loud things sound to us for a lot of different reasons. One of them is the equal loudness contours  (a 3 kHz sine wave at 100 dB SPL is painful whereas a 20 Hz sine wave at 100 dB SPL is starting to have some nice bass), another is temporal ( (a 3 kHz sine wave at 100 dB SPL is painful whereas a 1 ms click at 100 dB SPL is noticeable, but not worrisome). So, the "how loud things sound" definition of loudness results in measurements like "sones" which are related to dB SPL, but weighted with frequency - for example.

The "loudness" they're talking about in this article is the second definition - which should help to make things make more sense.

Cheers
-geoff

Beobuddy
Top 25 Contributor
Utrecht, The Netherlands
3,843 Posts
OFFLINE
Founder
Beobuddy replied on Fri, Jan 29 2021 10:00 AM

Thank you Geoff for taking time to help solving my confusion.

Btw. My compliments for the entertaining informative films you've made so far on Youtube. I regularly suggest these films to people who want to know a bit more about what happens inside their rooms with the acoustics.

Are there any new episodes to be expected?

Page 1 of 1 (4 items) | RSS
Beoworld Security Certificate

SSL