1. Audio Revamped Version

2. Introduction

3. All sound waves are analog in nature, made of an unbroken line without individually distinguishable pieces or components forming the sound wave This contrasts to digital signals, which break the wave into many individual components that approximate or mimic the shape of the wave All other media are primarily visual, while sound is perceived through the different sense of hearing It is a complex mixture of physical and psychological factors which is difficult to model accurately

4. Introduction All sound waves are analog in nature, made of an unbroken line without individually distinguishable pieces or components forming the sound wave This contrasts to digital signals, which break the wave into many individual components that approximate or mimic the shape of the wave All other media are primarily visual, while sound is perceived through the different sense of hearing It is a complex mixture of physical and psychological factors which is difficult to model accurately

5. 5 Sound wave The pattern of sound wave, usually displayed as a two-dimensional graph of pressure or amplitude against time For periodic waveforms, a single cycle or period defines the waveform. Also called sound pressure function, particularly when represented digitally Digital sound is a sound that has been converted to or created (synthesized) in a discrete form (numeric values) suitable for storage and processing in a computer

6. 6 Principles of Sound Sound can be describes as oscillations (ayunan, buaian, getaran) of air pressure that stimulate the eardrum to the auditory nerves and the brain. The oscillations must occur in a range of frequencies and amplitudes. The hearing range of the average person is approximately 20Hz to 17KHz

7. 7 Sound waves in air A single-frequency sound wave traveling through air will cause a pressure variation in the air The air motion which accompanies the passage of the sound wave will be back and forth in the direction of the propagation of the sound

8. 8 The idea of tuning fork resemble those created by a pendulum Our ears are the main receptors for sound The eardrum forms a membrane that is connected to a body of liquid and is sensitive to pressure changes within certain wavelengths The pressure changes result in hydraulic action that is converted into the electrical signals ultimately interpreted by the brain as sound.

9. 9 Sound wave’s amplitude = sound’s intensity Sound wave’s frequency = the length of time taken for the wave to complete one entire cycle Measured in unit Hertz (a cycle per second) 1000 Hertz = 1 KHz = 1000 cycle per second

10. 10 Frequency The reciprocal value of the period; it represents the number of periods in a second and is measured in hertz (Hz) stand for a cycles per second (cps). [ 1 HZ = 1 cycle per second ] Determined by the length of time it takes the waves to complete one entire cycle. One cycle is when the wave goes up, down through the line and back up again to the starting point In Multimedia systems - make use of sound only within the frequency range of human hearing - audio (acoustic signals) - speech, music and noise (range between 20Hz to 20kHz). Every musical note has a related hertz value

11. 11 Amplitude The sound’s intensity or loudness Measure of the displacement of the air pressure wave from its mean or rest position It has to do with the distance above and below the centerline of the sound wave The center line is the horizontal line in the drawings below, it is zero degrees

12. 12 Psychology of Hearing The properties of frequency and amplitude have corresponding concepts in auditory perception: pitch and loudness Pitch: Pitch of sound depends upon the frequency of sound. The greater the frequency, the higher is the pitch and vice versa. It is the pitch of sounds that enable us to distinguished b/w a sound of man and woman or man and dog. Etc. sound of a woman is shrill due to high pitch. Sound of a dog is grave due to low pitch and low frequency.

13. 13 Pitch The subjective impression of frequency, in the same sense that loudness is the subjective sense of the amplitude of a sound The perceived pitch of a sound is just the ear's response to frequency Pitch is a psycho acoustic variable, and the degree of sensitivity shown to it varies widely with people The pitch of a tone or note allows it to be placed in a musical scale; thus notes of a scale are often called pitches, and given names (A, B, C, C#, doh, re, mi, etc.)

14. 14 Loudness: Corresponds roughly to the amplitude of the note. The perceived loudness of a sound depends on both the frequency and amplitude of the physical stimulus. Loudness is measured in decibels (dB) The smallest audible sound is 0dB. A sound 10 times more powerful is 10dB. Here are some common sounds and their decibel ratings: DecibelDESCRIPTION 140 dBA gunshot or fire cracker 120 dBA rock concert or a jet engine 110 dBA car horn 90 dBA lawnmower 60 dBNormal conversation 15 dBA whisper 0 dBNear total silence

15. 15 Loudness Human ears measure the distance the ear drum moves when we hear a sound. The message is sent to the brain The brain translates the amplitude into the loudness of the sound Loud sounds have a large amplitude. They make the ear drum vibrate very far Soft sounds have a small amplitude. They vibrate the ear drum very little If the vibration is too small or too large, a person cannot hear the sound

16. 16 Digital Audio The most common form of digital audio is the compact disc (CD) Digitizing an analog waveform involves breaking it up into many small pieces that can later be lined up together to form a close approximation of the original, continuous signal The more samples that are taken, the more pieces are used to recreate the signal resulting in a higher resolution signal Digital audio is high-quality signals that suffer from very little distortion and noise compared to analog signals

17. 17 Analog to Digital Converter (ADC) Electronic equipment used to change or convert an analog (waveform style) signal into a digital signal (made up of 1s and 0s) The job of the analog-to-digital converter is to take the waveform (the analog signal) and split it up into the thousands of tiny "stairs" which simulate the wave Analog signals are converted to digital signals for a variety of reasons including to improve processing power (the ability to manipulate the signals), to encode analog signals for later playback through a digital medium (such as a CD or DVD) etc.

19. 19 Why is it important to change from analog to digital? Computer is in digital format To get clearer, precise audio without noise Noise can be cut / reduce by using digital. (ability to edit) Quality of data when transmitted – especially for long distance transmission.

20. 20 Sampling rate Describes how often samples are taken Every nth fraction of a second, a sample of sound is taken and stored as digital information in bits and bytes Three sampling frequencies most often used in multimedia are CD quality 44.1 kHz, 22.05 kHz and 11.025 kHz.

21. 21 Sampling size The amount of information stored about each sample. The more often you take a sample and the more data you store about the sample, the finer the resolution and quality of the captured sound when it is played back. Sample sizes are either 8 bits or 16 bits.

22. 22 Quantization The process of converting the sample amplitude to bits of data Value of each sample is rounded off to the nearest integer It can produce an unwanted background hissing sound

23. 23 Clipping If the amplitude is greater than the intervals available, clipping of the top and bottom of the wave occurs. Clipping may severely distort the sound.

24. 24 Digital to Analog Converter (DAC) Electronic device that decodes digital data (ones and zeroes) into an analog waveform electrical signal Digital signals from formats such as CDs and DVDs are converted from their digital form into an analog form in order for the amplifier and speaker to recreate sound Most digital playback devices (CD, DVD, laserdisc, etc.) include a digital-to-analog converter

25. 25 Editing Digitized Sound A number of software application are designed especially for digital sound editing and modification Software that can be used to edit digital sound :-  Sound Edit  SoundForge  Adobe Audition  Real Audio Encoder  Cybersound Sound FX  Camps  MidiScan  Webtracks

26. 26 File Size versus Quality Sampling rate determines the frequency makeup of the recording Sampling at higher rates more accurately captures the high frequency content of your sound Using more bits produces a recording that sounds more like the its original. Stereo recordings are more lifelike and realistic because human beings have two ears. Mono recordings are fine but tend to sound a bit “flat” and uninteresting when compared with stereo recording. Stereo sound files require twice as much storage space as mono files for the same length of time.

27. 27 Sound files can be edited in a large number of ways :- Amplitude adjusted Echo effect can be added Pitch can be shifted Various filters can be applied Softening / Sharpening the quality of the sound Trimming / combining and rearranging clips Format File Type : WAVE (Waveform Audio File) File extension:.wav WAVE is a proprietary Standard originally developed by Microsoft and IBM as part of the Resource Interchange File Format (RIFF) for Window 3.1.

28. 28 Common File Types Used for Digitized Sounds.aif.au.ram.mp3.mid/midi

29. 29 Adding Sound to Your Multimedia Project  Decide what kind of sound is needed (such as background music, special sound effects and voice over.). Decide where these audio events will occur in the flow of your project  Fit the sound cues into your storyboard, or make up a cue sheet  Decide where & when you want to use either digital audio or MIDI data  Acquire source material by creating it from scratch or purchasing it. (Be careful of copyright issues)  Edit the sounds to fit your project  Test the sound to be sure they are timed properly with the project’s images.