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3.3 UNDERSTAND SOUND IN MULTIMEDIA

Use sound in a multimedia project.Use MIDI and understand its attributes, especially relative to digitized audio.Calculate sampling sizes and considerations for digitized sound.Record, process, and edit digital audio.Determine which audio file formats are best for use in multimedia projects.Manage audio files and integrate them into multimedia projects.OUTLINEWHAT IS SOUND?A complex relationship involving a vibrating object (sound source), a transmission medium (usually air), a receiver (ear) and a preceptor (brain).

Vibrates bumps into molecules of the surrounding medium pressure waves travel in all directions

Sound are rapid vibrations that are transmitted as variations in air pressure.

SOUND WAVEFORMSSOUND WAVES

PROPERTIES OF SOUND WAVESNumber of wave vibrations per second; 1 Hertz is one cycle per secondThe faster the sound source vibrates, the higher the frequency.

1. FREQUENCY2. AMPLITUDE

MIDI (MUSICAL INSTRUMENT DIGITAL INTERFACE)MIDI is a standard for specifying a musical performanceRather than send raw digital audio, it sends instructions to musical instruments telling them what note to play, at what volume, using what sound, etc.The synthesiser that receives the MIDI events is responsible for generating the actual sounds. Example: Keyboard Piano

MIDI VS DIGITAL AUDIOTHE ANALOGUE TO DIGITAL CONVERTER (ADC)ADC is a device that converts analogue signals into digital signalsAn analogue signal is a continuous valueA digital signal is a discrete valueThe process to convert the analogue to digital sound is called Sampling. Use PCM (Pulse Code Modulation)

Air pressurevariations

Captured viamicrophone

Air pressurevariationsADCSignal isconverted intobinary(discrete form)01010011010110101111Analogueto DigitalConverterDACConverts back into voltageDigital toAnalogueConverterCAPTURE AND PLAYBACKOF DIGITAL AUDIOSampling RateFrequency of sampling (Hz)The higher sampling rate, higher quality sound but size storage is big.

2.Size sampleThe resolution of a sample is the number of bits it uses to store a given amplitude valueA higher resolution will give higher quality but will require more memory (or disk storage)

SAMPLINGThe answer will be in bytesWhere:sampling rate is in HzDuration/time is in secondsresolution is in bits (1 for 8 bits, 2 for 16 bits) number of channels = 1 for mono, 2 for stereo, etc.

CALCULATING THE SIZEOF DIGITAL AUDIOExample:Calculate the file size for 1 minute, 44.1 KHz, 16 bits, stereo soundSampling rate is 44,100 HzDuration/time is 60 secondsResolution is 16 bitsNumber of channels for stereo is 2

Answer: 10.59MB Sound ForgeDIGITAL AUDIO EDITING SOFTWARE

AudacityDIGITAL AUDIO EDITING SOFTWARE

EDITING DIGITAL AUDIOAUDIO FORMATSHOW AUDIO CAN BE USED EFFECTIVELYADVANTAGES AND DISADVANTAGES OF USING AUDIOTHANK YOU!