Dynamic range question, Dynamic range of hearing vs. equipment Options

[thesurfingalien]

Hi All,

I am having problems understanding the concept of dynamic range, and more specific how the dynamic range of human hearing relates to the dynamic range as specified for audio equipment.

What I have read on the Net is that the dynamic range of human hearing is, on average, 135 dB (the pain limit / threshold?).

I also understand that the dynamic range of a CD (16 bit) is limited to 96 dB, and for HD (24 bit) recordings 144 dB. This dynamic range is calculated by the bit-depth.

For playback of music (I use 44.1/16 flac only) I use a E-MU 1820 that has a dynamic range of about 115 dB (or so). I am not sure what my amp can do...

However, when I play music I hardly pass 80 dB (or so) listening volume, so the 96 dB CD data (if the recording makes full use of the range that is) gets "compressed", while the relative dynamic range remains.

After the long intro my question in essence is:

Does the human hearing have a similar "resolution" that is comparable to the resolution defined by the bit-depth in (digital) audio? Or am I just comparing apples and pears?

Regards,
Peter

[DigitalMan]

@Soap - agree we've not given thesurfingalien an answer they can digest (plus we got off topic which doesn't help.....) I'll take a shot based on your observations...

@thesurfingalien - Remember that as we increase the number of bits of resolution, all we're really doing is reducing the size of the error in representing (measuring) the waveform at each sample. In your 4-bit example, with only 16 distinct amplitude levels (2^4 = 16), you can picture that a few things will be true:

1) We don't have very many measurement levels, so we'll have to pick the level that is closest to the waveform during that sample and accept that there will be an error. This error will lead to effectively adding noise when we play back the sample.
2) The error will be different for every sample - some times we'll get it exactly right with our lowly 4-bit system but usually we'll be off as much as 1/2 of level (or, halfway between levels; any more than that and we should pick the next level). The amount of the error should be random across the range of zero to 1/2 of a measurement level for each sample in a well designed analog to digital conversion system (using dither, etc.), so the noise added during playback will also be random, leading to a white noise addition to the playback (white noise is the sound of pure randomness).
3) The ratio of how loud the white noise is due to the errors vs. the music signal (that ratio being equal to the dynamic range) will depend on how many measurement levels we have - basically the errors get smaller the more bits we have to accurately measure the waveform which leads to a lower level of noise vs. the signal and an improved dynamic range.

Also remember that in audio recording, the dynamic range of the recording is related to the ratio of the largest signal to the noise floor. The playback dynamic range is a totally separate discussion. The level recorded on a CD does not correspond to a volume level in playback due to variations in how loud you're playing it, the listening environment, etc. So these ratios define the dynamic range of the recording system (in this case its the CD). There is also the idea of whether the playback system can reproduce a 96dB or greater dynamic range using the same ideas - noise floor vs. loudest signal. It is possible that even with a 24 bit recording system we would have a tough time finding a playback system that could reproduce the 24 bit dynamic range for the listener (that is ~144dB, after all).

Does that help or just muddy the water more?