Sine wave: Difference between revisions

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=={{header|Emacs Lisp}}==

Note that this code does not work on Windows because playing sound from Emacs Lisp data variables is not supported there.

===8-bit samples===

<lang lisp>(defun play-sine (freq dur)

"Play a sine wave for dur seconds."

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(play-sine 440 5)</lang>

While the generated AU sound file is 16 bit, the samples themselves are 8 bit because only their high byte is set by the sine function. Therefore you will hear some faint hiss in the background due to the higher noise floor of 8-bit audio.

===16-bit samples===

This (slightly slower) version of the function creates proper 16-bit samples by setting both high and low bytes, resulting in less playback noise.

<lang lisp>(defun play-sine16 (freq dur)

"Play a sine wave for dur seconds."

(setq header (unibyte-string ; AU header:

46 115 110 100 ; ".snd" magic number

0 0 0 24 ; start of data bytes

255 255 255 255 ; file size is unknown

0 0 0 3 ; 16 bit PCM samples

0 0 172 68 ; 44,100 samples/s

0 0 0 1)) ; mono

(setq v (mapcar (lambda (x)

(mod (round (* 32000 (sin (* 2 pi freq x (/ 44100.0))))) 65536))

(number-sequence 0 (* dur 44100))))

(setq s (apply #'concat header (flatten-list (mapcar (lambda (x)

(list (unibyte-string (ash x -8))

(unibyte-string (mod x 256))))

v))))

(play-sound `(sound :data ,s)))

(play-sine16 440 5)</lang>

=={{header|Go}}==