Sound

Sound

 Importance of sound



 How to make sound (types)



 How to record and edit sound on your

computer



 How to incorporate sound in your MM work

Intro to Sound

We rely on SOUND to enhance Multimedia

Applications

WHY?

Easily capture the attention of users

Facilitate easy learning

Set the mood

On the Web, sound offers

 Background music, narration, and sound effects

Create moods

 Recorded testimonials from customers are used to market and sell

products and services. Interviews with rock stars and listening to a sample

of their music

 One-way audio offers on-demand radio listening around the world.

These radio programs broadcast music, talk shows, and live interviews.

 Internet Audio Conferencing or Internet telephony that allows two-way,

full-duplex audio conversations over the Web. With Internet telephony you

can talk to friends or family without the cost of a long-distance phone call.

What is Sound?

Sounds are pressure waves of air



Visualize the sounds as a series of

recurring waves called a waveform.



Volume - the higher the wave the higher

thesound



Pitch or frequency number of cycles

per second (cps), or Hertz

Play audio clip









Bells Oh

Sources of Sound

Pre-packaged

• Some sound files may come with your computer's operating system or with programs that

are installed on your computer.



Purchased or Borrowed

• Download from stock companies – $$$ or provided free



Create Your Own Sound Clips

• Recording program with a computer's operating system (such as Sound Recorder) and

speak into a microphone attached to the computer – quality will not be the best

• Recording studio with equipment such as DAT (Digital Audio Tape) devices that record

sounds digitally. Produces a high quality commercial product

• Electronic instruments such as synthesizers can be used to create music sound files.

Connecting the instrument to a computer allows the sounds to be captured in a MIDI

(Musical Instrument Digital Interface) format.

How is Sound Recorded?





(electrical signal)

analog



•Microphone translates •Analog-to-Digital

movement into electrical Converter (ADC). The ADC

signals (analog). Then captures a snapshot of the

tape recorder translates electric voltage on an audio

the waveform from an line and represents it as a

electrical signal on a wire, digital number that can be

to a magnetic signal on a sent to a computer.

tape (analog)

How is Sound Recorded and Played?

What is Digital Format?

 In a multimedia application sound must be in a digital form (string

of 1s and 0s).

 A sound can be recorded directly in digital form or an analog

sound can be converted to a digital sound.



 To convert analog sounds to digital sounds a technique is used

called digital sampling

Digital audio sampling I

 Sampling: is converting the

sound wave to numbers

using the magnitude of the

wave. That is from analog to

digital. How?

 Divide the horizontal axis

(the time dimension) into

discrete uniform pieces.

 Sample rate (frequency): is

how often the samples are

taken (fraction of a second)

Digital audio sampling II

 Sample size: the amount of information stored about

each sample 8 or 16 bits .

 Quantization – divide the vertical axis (signal

strength) into pieces. Sometimes, a non-linear

function is applied.

 – 8 bit quantization divides the vertical axis into 256

levels. 16 bit gives you 65536 levels.

 How many Samples to take?

 11.025 KHz — Speech (Telephone 8KHz)

 22.05 KHz — Low Grade Audio (WWW Audio, AM

Radio)

 44.1 KHz — CD Quality

Nyquist’s Sampling Theorem

For lossless digitization,

the sampling rate

should be at least twice

the maximum frequency

responses.



 Indeed many times

more the better.

Memory Required for 1 Minute

of Digital Audio

Digital audio

 It is the actual representation of

sound stored in the form of digital

numbers (Samples)



 It represents the loudness of the

sound at a slice of time



 It sounds the same every time

played.

Reasons to use digital audio

 It is consistent: the digital media will sound as

good at the end as it did in the beginning when

it was created.



 A wider selection of application software and

system support for digital audio is available.



 The preparation and programming required for

creating digital audio do not demand

knowledge of music theory; working with MIDI

data usually does require familiarity with

musical scores, keyboards, and notation as

well as audio production.

When to use digital audio

 You don’t have control over playback

hardware.



 You have the computing recourses

and bandwidth to handle digital files.



 You need spoken dialog.

Preparing digital audio files

 Two important aspects have to be taken in

considerations while preparing sounds:

1. Balancing the sound quality with the available

hardware resources.

Remember the relation between sampling frequency

and sound quality?

2. Setting proper recording levels to get clean

recording. If Recording level too high, it will

introduce noise. Conversely if it is too low it is

useless.

QUALITY OF DIGITAL RECORDING

 DEPENDENT ON

1. Sample Rate

2. Sample Size

3. Channels

4. Codecs

QUALITY OF DIGITAL RECORDING

Channels

 Mono signal

one stream of data reproduced equally on both speaker

channels

Lose stereo separation

 Stereo signal

consists of two streams of data working together

(left,right)

double the size of mono file

QUALITY OF DIGITAL RECORDING

CODECS



 Software programs that greatly

compress the audio file size



 Codecs use lossy compression by



 Removes redundant and less-significant

data

QUALITY OF DIGITAL RECORDING

Quality

How big can audio get?

 An example of uncompressed sound with CD

quality for 1 minute of audio:



 1 minute of recording  60 seconds

 60 * 44,100 samples/second  2,646,000

samples

 2,646,000 samples * 16bits per sample 

42,336,000 bits

 42,336,000 bits * 2 (stereo, 2 channels) 

84,672,000 bits

 84,672,000 bits / (8bits per byte)  10,884,100

 About 10 MB (Megabytes)!!!

Musical Instrument Digital Interface

MIDI sounds

 Allows sounds synthesizers from different

manufacturers to communicate with each other by

sending messages along cables connected to

devices.



 MIDI is a standard for encoding music, not sound. That

is a shorthand representation of music stored in

numeric form



 Contains instructions for creating the frequency, volume and

duration of notes that sound like various musical instruments



 MIDI files are recording of musical actions for

example:

 Pressing a piano key.

Midi versus digital audio

 MIDI files are much more compact than digital audio files.

The size of a MIDI file is completely independent of

playback quality.

 In general, MIDI files will be 200 to 1,000 times smaller

than CD-quality digital audio files. For example:

 MIDI

 21KB, 2min 36s

 Digital Audio

 612KB, 56s

 Because MIDI files are small, they don’t take up as much

RAM, disk space, and CPU resources.

 Which one is a live recording and which one is computer

generated? Can you tell the difference?

 One

 Two

Where to use Midi

 Because they are small, MIDI files

embedded in Web pages. When loaded,

MIDI files play more quickly than their

digital equivalents.

 Midi files are editable, thus it can be used

in the application where it might be needed

to change the length of the file without

changing the quality of the audio quality.

 Digital audio wont work because you don’t

have enough RAM, hard disk space, CPU

processing power, or bandwidth.

 don’t need spoken dialog.

Disadvantages of using MIDI files

 You can’t be certain that playback will be

accurate if the MIDI playback device is not

identical to the device used for production.

 Does not produce high-quality vocals

 Even with the General MIDI standard the

sound of a MIDI instruments varies according

to the electronics of the playback device and

the sound generation method it uses.

 Also, MIDI cannot easily be used to play back

spoken dialog.

Components of a MIDI System

 Synthesizer:

 It is a sound generator (various pitch, loudness, tone

colour).

 A good (musician’s) synthesizer often has a

microprocessor, keyboard, control panels, memory, etc.

 Sequencer:

 It can be a stand-alone unit or a software program for a

personal computer. (It used to be a storage server for

MIDI data. Nowadays it is more a software music editor

on the computer.

 It has one or more MIDI INs and MIDI OUTs.

 Track:

 Track in sequencer is used to organize the recordings.

 Tracks can be turned on or off on recording or playing

back.

Components of a MIDI System

 Channel:

 MIDI channels are used to separate information in a MIDI

system.

 There are 16 MIDI channels in one cable.

 Channel numbers are coded into each MIDI message.

 Timbre:

 The quality of the sound, e.g., flute sound, cello sound, etc.

 Multitimbral – capable of playing many different sounds at the

same time (e.g., piano, brass, drums, etc.)

 Pitch:

 musical note that the instrument plays

 Voice:

 Voice is the portion of the synthesizer that produces sound.

 Synthesizers can have many (12, 20, 24, 36, etc.) voices.

 Each voice works independently and simultaneously to produce

sounds of different timbre and pitch.

 Patch: the control settings that define a particular timbre.

Making MIDI audio

 To make MIDI audio you need:

 Sequencing software

 Sound synthesizer

 A MIDI keyboard

 Instruments that can be synthesized are

identified by general MIDI numbering

system that ranges from 0 to 127

 Good sequencing software allow printing

and scanning the music sheets.

Adding sound to MM project

Steps to bring audio recording into MM

project

 Decide what kind of sound in needed (such

as background music, special sound effects,

and spoken dialog).

 Decide where these audio events will occur in

the flow of your project.

 Fit the sound cues into your starboard, or

make up a cue sheet.

 Decide where and when you want to use

either digital audio or MIDI data.

Other steps

 Acquire source material by creating it

from scratch or purchasing it.

 Edit the sounds to fit your project.

 Test the sounds to be sure they are

timed properly with the project’s

images. This may involve repeating

previous steps until everything in

sync.

Editing digital recording

 Once recording and digitizing been

made, editing will be made. Following

are list of editing operations that are

most used:

 Trimming: removing blank space from

the beginning and extra time at the end.

 Splicing and assembly: putting short

segments to gather in a longer one.

Other editing operations

 Volume adjustment: when assembling

different segments in one, the volume

may be not the same, thus it is

important to be able to adjust the sound

volume.

 Format conversion: one should be able

to convert audio files from one type of

files to types that director plays. It plays

AIFF, SWA, AU, or WAV audio files.

Other editing operations

 Resambling or downsampling: If you

have recorded your sound at 16-bit

sample size but are using lower rates

in your project, then you must edit

the file downsasmpling its contents.

 Fade-ins and fade-outs: beginning

and ending the sound gradually and

in a smooth way.

More editing operations

 Equalization: allow modifying recorded

content to sound brighter or darker.

 Time stretching: some programs allow

alter the length of the sound file

without changing the pitch(‫)النغمة‬

 Digital signal processing: add special

sound effects

 Reversing sound

Sound-Editing Software - cont







Audacity Software

Edit the clip,

Combine it with other

sound files Add

transitions or special

effects

Sound-Editing Software - cont









Recording sound using

WaveStudio









Edit the clip,

Combine it with other sound files Add

transitions or special effects

Adding sounds

Uses for adding sounds

 We can mix sounds

 We even know how to change the

volumes of the two sounds, even over

time (e.g., fading in or fading out)

 We can create echoes

 We can add sine (or other) waves

together to create kinds of

instruments/sounds that never

existed in nature, but sound complex

Sound File Formats

Sound File Formats - continued





So which format is best?









uncompressed