Image and Sound Editing

Raed S. Rasheed2012

Digital Sound

• Pitch digital sound• Echo digital sound• Fade in digital sound• Fade out digital sound

Pitch digital sound

• Is the process of changing the speed or duration of an audio signal. The simplest way to change the duration or pitch of a digital audio clip is to resample it. This is a mathematical operation that effectively rebuilds a continuous waveform from its samples and then samples that waveform again at a different rate. When the new samples are played at the original sampling frequency, the audio clip sounds faster or slower

Pitch digital sound

Pitch digital soundALGORITHM Sound_Pitch 8.101 INPUT Sound, rate02 OUTPUT NewSound03 BEGIN04 Create new sound file NewSound;05 SET index = 0, c = 0;06 WHILE index < Sound.Length07 SET i = tranc(index);08 SET frac = index - i;09 SET S1 = Sound[i];10 SET S2 = Sound[i+1];11 SET NewSound[c] = S1 + ( S2 – S1) * frac;12 SET c = c+1;13 SET index = index + rate;14 END WHILE15 RETURN NewSound;16 END

Echo (Reverb ) digital sound

• is the persistence of sound in a particular space after the original sound is produced. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air.

Echo (Reverb ) digital sound

Echo (Reverb ) digital soundALGORITHM Sound_Echo 8.201 INPUT Sound, delay, decay02 OUTPUT NewSound03 BEGIN04 SET delaySample = delay;05 SET i = 0;06 WHILE i < Sound.Length 07 IF i < delaySample THEN08 SET NewSound[i] = Sound[i];09 ELSE10 SET NewSound[i] = Sound[i] + Sound[i - delaySample] * decay;11 END IF12 SET i = i + 1;13 END WHILE14 RETURN NewSound;15 END

Fade in digital soundALGORITHM Sound_FadeIn 8.301 INPUT Sound02 OUTPUT NewSound03 BEGIN04 SET decayRate = 1 / Sound.Length;05 SET decay = 0;06 SET i = 0;07 WHILE i < Sound.Length08 SET NewSound[i] = Sound[i] * decay;09 SET i = i + 1;10 SET decay = decay + decayRate;11 END WHILE12 RETURN NewSound;13 END

Fade out digital soundALGORITHM Sound_FadeOut 8.401 INPUT Sound02 OUTPUT NewSound03 BEGIN04 SET decayRate = 1 / Sound.Length;05 SET decay = 1;06 SET i = 0;07 WHILE i < Sound.Length08 SET NewSound[i] = Sound[i] * decay;09 SET i = i + 1;10 SET decay = decay - decayRate;11 END WHILE12 RETURN NewSound;13 END