Noise that never ends

[Stav]

I went to a Physics lecture type thing in London about 5 years ago at school, and one of the lecturers played a sound that 'sounded' like it was getting higher all the time, but in fact it would never get out of our hearing range, and could go on forever. Can anyone either explain this and/or link to a site that maybe has this sound on it?

[xyzzy@bok]

What, does it sound a bit like a siren starting up? i had a wav file like that once for Start Windows, i think it was called gliss or something.. i reversed it in audacity then spliced, so it wound down again, or it would have gone on forever! Or is your one much more complex? is it a loop? :-)

[xyzzy@bok]

here's another weird sound.. http://theremin.info/

[MadScientist]

if the sound was increasing linearly it would either have to stop or go beyond your hearing range. (approx 15Khz I think depending on your age!).
If the frequency was increasing logarithmically though it would continually increase but never go beyond an audible frequency.Though, the higher and higher the frequency went, the more difficult it would be to hear it changing.

[xyzzy@bok]

Third time lucky.. this one's it.. i think :-) http://www.sm.u-bordeaux2.fr/~psyac/gliss.html

[Stav]

I dont remember all that much. I think the sound just fooled us into thinking it was getting higher somehow, but in fact it never was at all. It might have sounded a bit like a siren, but i vaguely remember it being quite a mixture of sounds. Sorry I cant be more help!

[Stav]

I found it! Its called Shepard's tone! Not found a good download yet though. I found a link that explains it, but the links to the sound itself dont work. If anyone find a woking mp3 or something, please post a link here. http://icg.harvard.edu/~scia49/demonstrations/spir
al.html

[kahunabean]

I think I saw something similar - at the Toronto Science Museum maybe 24 years ago (!) It was a display where a device with a speaker made a pulse tone which *sounded* like each tone was higher than the last. There wasn't an explanatory note ! (It was meant to be a brain teaser). The only thing i caould think of was that it was an "aural illusion". I think each tone drops in pitch slightly towards the end each pulse. That way, the next tone, starting fresh, sounds higher than the last. In fact, its the same pitch each time, but each pulse tails off slightly - leading to the "illusion".

[j2buttonsw]

Isn't there a bit on the end of an old Queen album where Brian May does a similar thing on guitar?

[Pickle]

That's a musical question. The sound works by having a lot of notes, all an octave apart, all playing together. All the notes gradually get higher until the one at the top (the highest pitch) goes out of hearing range. At this point it is replaced by a note at the lowest pitch. The change is imperceptible and gives the illusion that the note is constantly rising.

[DMAC1144]

It's on the site below http://www.cs.ubc.ca/nest/imager/contributions/fli
nn/Illusions/ST/st.html Once the page loads a little Java Applet loads at the top of the page. You can make the sound ascend or descend. Very interesting. Mind you, you can hear the point where it loops and it never really gets all that high or low... still good though.