# What's that noise on cassettes?
**URL:** https://boards.straightdope.com/t/whats-that-noise-on-cassettes/152368
**Category:** Factual Questions
**Created:** [February 2, 2003, 9:36pm UTC](https://boards.straightdope.com/t/whats-that-noise-on-cassettes/152368 "2003-02-02T21:36:34Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Minor\_Irritant](https://boards.straightdope.com/u/Minor_Irritant)
#### Post date: [February 2, 2003, 9:36pm UTC](https://boards.straightdope.com/t/whats-that-noise-on-cassettes/152368/1 "2003-02-02T21:36:34Z")
I popped an old cassette into the tape deck the other day, after not listening to one for years. When it came to the end, it emitted a high-pitched noise for a few seconds. Flipping it over, the same noise was heard at the beginning.
I’ve heard this noise on a variety of tapes - why is it there?
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### Author:  [@Seven](https://boards.straightdope.com/u/Seven)
#### Post date: [February 2, 2003, 9:43pm UTC](https://boards.straightdope.com/t/whats-that-noise-on-cassettes/152368/2 "2003-02-02T21:43:35Z")
Some commercial cassettes had a frequency test tone on the tapes. It was about 7 tones. Is that what you’re hearing?
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### Author:  [@ftg](https://boards.straightdope.com/u/ftg)
#### Post date: [February 2, 2003, 9:46pm UTC](https://boards.straightdope.com/t/whats-that-noise-on-cassettes/152368/3 "2003-02-02T21:46:25Z")
The “glue” that binds the magnetic material to the tape has bled thru. Some people have “baking” remedies but I’ve never seen one work. I consider such tapes a loss.
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### Author:  [@Minor\_Irritant](https://boards.straightdope.com/u/Minor_Irritant)
#### Post date: [February 4, 2003, 10:48pm UTC](https://boards.straightdope.com/t/whats-that-noise-on-cassettes/152368/4 "2003-02-04T22:48:06Z")
> [@](#):
>
> \*Originally posted by Seven \*
> \*\*Some commercial cassettes had a frequency test tone on the tapes. It was about 7 tones. Is that what you’re hearing? \*\*
That must be it, as it steadily changed in pitch. It sounded too “clean” to be the product of degradation.
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### Author:  [@ianzin](https://boards.straightdope.com/u/ianzin)
#### Post date: [February 4, 2003, 11:15pm UTC](https://boards.straightdope.com/t/whats-that-noise-on-cassettes/152368/5 "2003-02-04T23:15:27Z")
I think I know this. It’s an acoustic marker put on the master tape from which the cassette copies are made. It tells the machine that duplicates the cassettes when Side 1 ends and Side 2 begins so it can reverse and lay down the second side. This is all done at high speed, of course.
An industrial cassette-tape duplication plant once opened up opposite a place I worked, and I went across to have a chat and see how it was done. The equipment involved was pretty awesome. Anyway, that’s what the guy said that little wibble-wobble tone was for.