Inside Macintosh: Sound /

Chapter 4 - Speech Manager / Speech Manager Reference

Speech Manager Routines / Changing Speech Attributes

SetSpeechPitch

You can use the SetSpeechPitch function to set the speech pitch on a designated speech channel.

FUNCTION SetSpeechPitch (chan: SpeechChannel; pitch: Fixed)
                           : OSErr;

chan

The speech channel whose pitch you wish to set.

pitch

The new pitch for the speech channel, expressed as a fixed-point frequency value.

DESCRIPTION

The SetSpeechPitch function changes the current speech pitch on the speech channel specified by the chan parameter to the pitch specified by the pitch parameter. Typical voice frequencies range from around 90 hertz for a low-pitched male voice to perhaps 300 hertz for a high-pitched child's voice. These frequencies correspond to approximate pitch values in the ranges of 30.000 to 40.000 and 55.000 to 65.000, respectively. For information about the mathematical relationship between pitches and frequencies expressed in hertz, see "Speech Attributes" beginning on page 4-6. Although fixed-point values allow you to specify a wide range of pitches, not all synthesizers will support the full range of pitches. If your application specifies a pitch that a synthesizer cannot handle, it may adjust the pitch to fit within an acceptable range.

SPECIAL CONSIDERATIONS

You can call the SetSpeechPitch function at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SetSpeechPitch function are

Trap macro	Selector
_SoundDispatch	$044C000C

RESULT CODES

noErr	0	No error
invalidComponentID	-3000	Speech channel is uninitialized or bad