I wanted to see if I could reproduce the apple 2 beep sound with the AY-3-8912. It's supposed to be around 1000hz, but that doesn't sound quite right if I'm using the apple2e driver as a reference.

Reading some Synetix SuperSprite documentation (Synetix SuperSprite Owners Manual.pdf page 40 of 266) it says that I just have to divide 63920.438 by the desired pitch.

Tone Period =1,022,727 / 16 X desired pitch
= 63,920.438 / desired pitch

so let's make a little function to calculate the tone:

Code
function calctone(freq)
return math.floor (63920.438 / freq)
end


then I can make something that sounds pretty close to the CTRL+G bell.

I came up with around 930 hz just by listening to the tone and hunting for a number that was close.

Code
add_func_string([[for i=0,0 do sound(7,24);settonevol(0,calctone (930),15); delay(6); settonevol(0,0,0); delay(1); end print("done")]])

but how close is that actually?

I fired up mame with the debugger and set a watchpoint on $c030 with

Code
wpset c030,1,r

and then typed g in the debug window.

Once the boot beep hit c030 I went to the lua console and typed:

Code
a = emu.time()
then hit g again in the debugger, and then got the time at that point:

Code
b = emu.time()

so how long did that take?

Code
print(b-a)

0.00053435114503789

so let's convert that to hertz:

Code
print(1/(b-a))
1871.4285714295

oh but wait, it should be half that since we've only counted half a tone cycle

Code
print(1/(b-a)/2)
935.71428571477

which I got pretty darn close to, 930 vs 936. Not bad for someone who's tone deaf.

Now I've got a beep that is pretty much identical.



Code
add_func_string([[for i=0,0 do sound(7,24);settonevol(0,calctone (936),15); delay(6); settonevol(0,0,0); delay(1); end print("done")]])

Last edited by Golden Child; 11/11/17 01:12 PM.