Snapping noise at end of audio stimuli

[Linda]

Hoping somebody has an idea on this one. On my stimulus slide, a 500ms tone is presented through Chronos paired with a visual target on the display. Participants respond as quickly as possible with a key press using Chronos. When testing the tone in Adobe Audition, it presents without any snap at the beginning or end, just a smooth tone. When testing in Audacity, there is a snap at the end of the tone, and this snap is also present when played through Chronos. The snap reliably occurs if the participant responds within 500ms, thus terminating the tone early. The snap almost always occurs if the participant responds later than 500ms (the tone snaps at 500ms followed by programming silence until 1500ms).

The question is if anybody else has had similar issue with a snapping sound at the termination of a tone (early or programmed) when played through Chronos (or even the computer, as I have used both). Anybody experience similar?

Better yet, anybody have a solution?

Thank you in advance.

[Michiel Spape]

Hi Linda,

I believe it has to do with audio itself. Being neither a physiologist nor physicist (just an occasional psychophysiologist and psychophysicist!), I’ll leave the exact explanation out, but if you think of a 100 Hz tone, so with a period of 10 ms, pressing the button at any point other than at precisely 0 ms and 10 ms cuts down the sine. The result is almost exactly the same as if you cut down the sine at the start: if you remove the first 2.5 ms of a 10 ms sine, it should be at maximum amplitude, right? So you hear a tick (of higher frequency). I believe what Adobe audition and most other programmes do is to avoid this annoying sound is to either start audio at zero crossings, or to put in tiny ‘ramp’, e.g. a 10 ms fade-in. When I first started working with vibrotactile stimuli applied to the fingers, I was told explicitly by my psychophysics teacher to always put in a ramp up and ramp down, because otherwise you can even feel a little tick on your fingers if you don’t apply sufficient envelope on your fade-in AND fade-out.

 

Hope that helps. Personally, I would keep the tone as continuing playing even after a participant presses the button, unless it’s absolutely necessary not to do so.

Best,

Michiel

--
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To unsubscribe from this group and stop receiving emails from it, send an email to e-prime+u...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/e-prime/f153c7b9-f612-4498-affa-05ed035c3a94n%40googlegroups.com.