Transient/peak question

asi9

New member
Why do you sometimes not hear transients? Let's say you're looking at a snare track in Soundforge. Sometimes the peak intensity just does match up with the actual loudness of the hit. I can see a really sharp peak for a snare hit that sounds rather weak or quiet, then see a snare hit that rings loud and clear that appears graphically to be 3 to even 6db quieter in volume.

Of course, I usually end up limiting/compressing the peaks that bring down overall volume, by why do they exist in the first place? Is there perhaps a really sharp frequency that's hot that I just don't hear well in whatever I'm listening through?
 
Thats because loudness as we perceive it is really more closely related to RMS volume. In other words, being transient in nature (ie short lived) the average volume (loudness) may be lower than another longer lasting sound with a lower peak.
 
Does that mean that's happens so fast, we really don't even notice/hear it at all? Kinda like if you were watching a movie, and you replaced one of the frames with a different image... at 40/50 frames+ per second, you would even register that different image?
 
Yeah, I think it has to do with the basic mechanics of hearing. The ear (if I can remember from one of Harvey's posts) is essentially a pressure gradient transducer. The pressure generated by a transient is small since it is so short lived, so it is not necessarily perceived as being loud.

Maybe someone else could add something......
 
Part of the reason (not all) why a sharp transient spike sounds relatively quiet is due to it's frequency spread. The duration of a wave actually effects it's spectrum. Say you take a pure 1kHz sine wave and just play one cycle. The spectrum of this sound is actually very broad. It no longer sounds like a pure tone.

I've attached the frequency spectrum of such a pulse to illustrate this. I'll post the mp3 file next.

When sound energy is spread over a broad spectrum we don't perceive it as being as loud as when the same amount of energy is concentrated in a narrow frequency band.

Cool stuff :cool:

barefoot
 
Damned thing removes the attachment if you preview.

Anyhow, here's the spectrum graph.
 

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  • pulse-spectrum.gif
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Damn.... just when I thought I was starting to get a good grasp on the mechanics and physics of sound, I am once again reminded with a bitch-slap of reallity that I don't know jack shit.
 
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