Create a smooth, normal-distribution like wave form.

Hi there folks!

I want to create a short (<1s) wave consisting of a maximum amplitude sound. To avoid clicking sounds, I want this wave shape to be as smooth as possible and starting and ending with silence — something very like a normal distribution. The first half of a sin wave starts a little bit too abruptly, and fading it in and out causes disruptions that are noticeable. Any help?

Rationale: my goal is to have a full volume, completely inaudible sound, as short as possible, to trick my speakers into thinking that something is playing. Otherwise, they go (hardwardly) to sleep, and loudly pop when waking up, preventing their use as an alarm in the morning.


Try fading in and out using the “Adjustable Fade” effect.
I think the “S-Curve In” and “S-Curve Out” presets will produce what you are looking for.

Does it need to be “full volume”? It can be a bit risky for the speakers to play very high amplitude sounds that are outside of their normal frequency range, but if, say “1/4 volume” works for keeping your speakers awake, you could try a low amplitude very low frequency sound - say 1 Hz for 1 second.

Thanks very much, this is precisely what I needed! To sum up: Each of Adjustable Fade > S-Curve {in, out} helps in providing half a normal distribution — they create a “double” curve that bends on both ends; combining them e.g. on a sine wave gives the desired shape.

As for it being risky, you are right, and I’ll experiment with the actual threshold (which should be around 35% on my Creative speakers).

Happy end-of-December! :slight_smile:

You’re welcome.

A bit of technical information that you may be interested in (or not :wink:)
The curve shape of the “S-Curve” setting is actually a raised sine wave. One property of this type of curve is that it has the lowest possible angular velocity throughout for a given amplitude change and duration - or in English, it is the smoothest transition that you can get, just as a circle has no corners and the smoothest possible curve for a given size shape.

Ahah, it is obviously interesting — considered in particular the amount of time I spent before asking here :slight_smile: I indeed searched for a way to raise a sin wave, to shift the amplitude somehow — I hopped at some point that I could non-symmetrically change the “envelope” to do so. I just noticed that the Range Translator tool is what I was searching for. Thanks again!

I’ve no idea what the “Range Translator” tool is, but it is very easy to “offset” a waveform using a “Nyquist command” in the Nyquist Prompt effect.

To raise the wavefom by +0.4 (linear scale), the command is:

(sum S 0.4)

To lower the waveform by 0.4, use the negative of 0.4:

(sum S -0.4)

The “S” symbol represents the selected sound in the Audacity track.
The “Adjustable Fade” effect is written in “Nyquist” code.