佢有道理，不過正常一般室內聽音樂大概70-80 dBA 音量，50dB 根本太細聲。所以dynamic range 約80-30=50 dB.
有些師兄可能開到90dBA, 已經頗大聲。而我懷疑流行曲演唱會的導演或監制心理一般有問題，我見過紅館近控制台去到120dBA. 那音响師仁兄話是道演丶監制要求的。我唔明咁大声有咩用？

http://www.harbeth.co.uk/usergroup/showthread.php?2161-Does-turning-up-the-volume-increase-dynamic-range

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Alan A. Shaw
Designer, owner
Harbeth Audio UK

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Coincidentally, the dynamic range of a wide-band classical recording may be roughly 40dB or so. I'll use slightly different numbers to avoid confusion. So working this through:

1) Heard live, the peak level has a sound pressure at the ear of 95dB, and the quietest orchestral sound (say) (95-40dB) = 55dB at the ear.

2) On replay at home, you arbitrarily set the volume control so that on playback the loudest sound has a sound pressure of 50dB at the ear in your listening room. You could have picked any level you like within the limitations of your system (and the law on noise nuisance); I'm just quoting the one you mentioned.

3) The dynamic range of the recording remains unaltered since the recording is burned into the CD and has no knowledge of how loud, where or when it will be played - if ever

4) The quietest sounds in the recording are, as noted, 40dB below the peak level (i.e. the recording has a dynamic range of 40dB). As you have set the home replay peak to 50dB at the ear, the quietest sound in the recording will have a pressure at the ear of (50-40dB) = 10dB.

5) We have to consider the background noise level in the listening room from the whirring sound of machinery, mechanical hum from mains transformers etc., air con, passing cars, wind, neighbours, conversations through the wall, passing aircraft, sirens, ticking clocks etc. etc.. These are noise sources and generate a significant background noise level - the equivalent to tape hiss. Add to that self generated noises inside the human ear and body, tinnitus, whistles, gurgling noises, blood pumping, heart beats etc..

6) The total cumulative level of these unwanted noise sources measured at the ear add up to a cumulative 30dB or whatever: they cannot be ignored and they are not insignificant.

7) No music signal can be heard when its energy drops below the background noise level (the same with tape hiss). Low energy elements of the music signal cannot compete with the higher energy noise, and will be swamped by it into inaudibility.

8) Therefore, in this example the actual dynamic range of the home listening experience is not the 40dB of the recording, but the peak music level at the ear of 50dB minus the background noise level of 30dB = 20dB. Remember: dynamic range is merely the difference between the loudest signal (50dB) and the quietest useful signal - since no music can be heard below the background noise floor, that defines the quietest usable signal.

So, the presence of the inevitable background noise (much higher in the city, lower in the countryside) always reduces the perceptible dynamic range of the replayed performance.

When a radio station targeted at listeners on the move (e.g. in a car) or playing at a low level as background entertainment in a shop or office, the engineers are acutely aware that the high ambient noise level will erase the quieter detail in the music. That's bad, but if it is a commercial station, that's a disaster. So, radio stations are transmitted with a deliberately compressed dynamic range in the audio signal and then the peak level taken up to the maximum legally permitted level according to their transmitting licence. Taking the above recording with its 40dB dynamic range, if this same performance is played over SuperPopFantastic FM, as the signal leaves their studio onward to the transmitter chain, the dynamic range will have been squeezed to perhaps no more than 6dB (!). Then, even if the radio is being played quietly at home, in the car or office, the lower energy audio elements will have been lifted (hopefully) above the ambient noise - advertisers will be delighted.

There is absolutely no point whatever chasing super high resolution audio (such as DACs that claim electronic noise levels of minus 120dB or whatever below peak level) unless you listen in an anechoic chamber because you simply cannot find a quiet enough environment at home to benefit from that degree of perfection. Bog standard CD with a noise floor of about -100dB below peak level (i.e. a dynamic range of about 100dB) is a far, far bigger dynamic range than we will ever need at home because of the background noise level.

How's that as an explanation of noise masking?

最後修改時間: 2016-03-12 02:45:31