Sound slows down in Flash.
Symptoms
The sound plays slower in Flash Designer. External player works fine.
Cause
MP3 or WAV sound does not match frequency allowed by Macromedia Flash format.Supported sampling rates: 44000 Hz, 22000 Hz, 11000 Hz, 5500 Hz
Unsupported sampling rates: 48000 Hz, 32000 Hz, 24000 Hz, 16000 Hz, 12000 Hz, 8000 Hz
Flash Designer will try to match sampling rate as close as possible. If the difference is relatively high the sound will play slower.
To verify sampling rate import the sound with "Movie" > "Import Sound". Select the sound and check sampling rate in Hz:
Example of unsupported frequency (8000 Hz)
Example of supported frequency (44100 Hz)
Solution
Use sounds at supported frame rates. Use external sound editor to resample sound file to requested frequency.Use Windows Sound Recorder to resample WAV files. Choose "Start" menu > "Run" and type "sndrec32.exe". Open your WAV file, choose "Save As" and click the button to change sound format. Select PCM format and the next lower frequency (for example if your sound is 32000 Hz, change it to 22000 Hz, for 24000 Hz choose 11000 Hz etc). Select bit count (8 or 16 bits) and stereo/mono option to match the source sound. If you don't know source values choose "File" > "Properties" command. To optimize file size you can downsample the WAV file to 8 bits / mono.