# A question of sound knowledge

Discussion in 'Electronic Basics' started by [email protected], Aug 17, 2004.

1. ### Guest

A student adds a sound output feature to their design using a small
sounder (about the size of your little finger) driven by a logic
output from a microcontroller.

The table of frequencies look like this:

100 Hz
200 Hz
300 Hz
400 Hz
500 Hz
600 Hz
700 Hz
800 Hz
900 Hz
1.0 kHz
1.1 kHz
1.2 kHz
1.3 kHz
1.4 kHz
1.5 kHz
1.6 kHz
1.7 kHz
1.8 kHz
1.9 kHz
2.0 kHz
2.1 kHz
2.2 kHz

Why is this wasteful and partly senseless?

Robin

2. ### Rich GriseGuest

Because nobody has any idea what you're talking about?

3. ### BanGuest

If you want useful sound, the frequencies should be logarithmically spaced
like
100Hz, 125Hz, 163Hz, 200Hz, 250Hz, 315Hz, 400Hz, 500Hz, 630Hz, 800Hz, 1k
1k25, 1k63, 2k, 2k5, 3k15, 4k
This will give the impression of equal rise throughout the range. It is easy
to detect and will give satisfactory results.

4. ### BanGuest

I overread the size, that thingy wouldn't give any audible output at 100Hz
unless you put it right next to the ear. Start with 500Hz or even higher and
use closer spaced intervals.
Your prof has the right approach, hope he doesn't flunk you. This world is a
bit more than digital and a student should know basic physics and mechanics
as well.

5. ### Michael A. CovingtonGuest

etc.

The upper frequencies in the range are going to be too hard to distinguish.
For equal distinguishability, you want equal ratios (100, 200, 400...), not
equal spacing.

6. ### John LarkinGuest

If he/she drives it with a square wave it sure will.

John

7. ### Guest

I hope you're wrong about that, but I fear not because something
very similar to the above has been in a commercial product for the
last ten years.

Cheers
Robin

8. ### Guest

....and this is why no one has noticed the sillyness of it (in the
commercial product that it lives in).

It also consumes excessive code. The same audible effects can be
produced a lot cheaper. [say five fundamentals? In geometric
progression, at the "useable" higher frequencies].

Robin

9. ### BanGuest

I fear it will then sound not much different with 300 or 500Hz, the latter
being one of the recommended frequencies.
The OP talks about a commercial product, what kind of commercial product is
it and have you really measured the outputted frequencies? I cannot believe
that there are used the stated frequencies.

10. ### JamieGuest

touch tone dialing?
i don't know.

11. ### Guest

That's what I say about MS Windows (as a former Acorn Archimedes user)
"I don't believe it, why would anyone buy one of these?" but the Arch'
is a commercial failure and the PC is a commercial success.

Robin