Ch 6 - Sistem Bunyi(bi)

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Sound : The perception of the dinamic convergence and vacuum air pressure level in ear. Audio : Produce from sound to electronic Sound wave : Generate from vibration/ shake. The air molecul near to the shaking source will shake too. Sound wave is produce when the molecul move reverse in position same with the shaking object. Amplitud & strength of sound : The number of moving molecul described the strength of sound and this is called – sound amplitud ( measured in dB ) Acoustic pressure is measured in Sound Pressure Level. Dinamic range : Range from silence sound level to a noisy sound level that can be heard. Monaural : Sound from Headphones Monophonic : Sound from speaker.

0 Hz

Sound Pressure Level (SPL) – Infrasound

20 Hz

* Po – Sound power level Hearing band (Sound Freq :

20kHz

∞

SPL = 20 log Po/ 2 x 10⁻⁵ dB

100 Hz ~ 5kHz) Ultrasound

2 x 10⁻⁵ - Min. pressure of sound Human hearing level - 0 dB-SPL to 120 dB- SPL ( ear will start feel the pain)

The Biology of Ear : • Divided to 2 area : i. External – Directional sound area (sound calyx) ii. Intermediate – Gegendang (reception of different type of sound freq) - Differentiate between human and the animal

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Mono system – Depand to one recording system and sound channel. i.e. – telephone system (monaural system). Whereas, radio broadcasting and sound system at cinema (monophonic system). Monaural : Sound from Headphones Monophonic : Sound from speaker. Info from mono system ≠ original info if the audience concentrate. Because the microphone pick the sound signal from one point whilst audience can hear sound from two points.

• Stereo system – audio system that produce sound

from 2 direction. • The good stereo system can produce sound illusion (position are fixed – cross the sound stage). In hi-fi system it is called stereo image. • User can separate and compare the sound o/p where the sound quality can be adjusted by considering the sound balance.

SISTEM QUAD • QUADRAPHONIC @ 4 audio speaker system. • To boost the stereo sound. • Better sound spreading compare to stereo sound system with 2 speaker. • Surround @ rear speaker – for environment sound. • This system are used to compressed the audio o/p. i.e Concert

L

Surround

C

R

Surround

Layout for stereophonic sound / Dolby Stereo 

Dolby Surround - New dimension of sound addition to common stereo sound. - Using Dolby MP Matrix Encoder ~ encod 4 audio channel to 2 audio channel for stereo broadcasting programme.

5.1 Channel System This system have 5 channel - frequency range from 3Hz to 20 KHz for front, left and right, center, surround o/p and additional of LFE (Low Freq. Effect) Sub-Woofer - freq range from 3 Hz to 120 Hz. Digital Media Producer / Mixer Multi Channel Audio

L C R

Dolby Digital Encoder

Ls Rs

Digital Bit Stream

A/V comp. with Dolby Digital decoder

L C R Ls Rs

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When sampling the wave with an analog-to-digital converter, two variables need to be controlled : The sampling rate - Controls how many samples are taken per second The sampling precision - Controls how many different gradations (quantization levels) are possible when taking the sample

P.A. system divided to 2 level : - High level system for

- Low level system

- wide area i.e Mosque, stadium and useful for place which is crowded with people - narrow area i.e. meeting room and place which have a few people only.

Divided to 3 category :A Category – Open area ~ audiens > 5000 B Category – Inside hall ~ audiens > 1000 C Category – Inside hall ~ audiens ≈ 500

COLUMN SPEAKER

HORN SPEAKER

Main Cluster Fill System MIC

Main Cluster Fill System Balcony MIC

Rear Fill System

Cover by rear fill system

• Determine the function and the reason why the audio system and the installation equipment is used. • Before start the equipment installation for audio system, detail planning is needed to understand the specification & cost estimation. • Others factor that relates is as below :Study the sound condition in the area. Audio system selection and the determine the position of installation. Draw the block diagram of the system, circuit diagram, arrangement &

Additional equipment in P.A. 1. Microphone - Convert acoustic energy to electric energy - Able to convert in same value --sound wave electric sound ---in wide range - Electrostatic, moving coil & ribbon

2.

Speaker - Mono speaker : give distance info only. - Stereo amplifier – give position info and separation sound. - Type of speaker :a. Moving coil - Common use. Able to stand overload / Coil place at the magnet chink. b. Piezoelectric - Good for high freq / i.e. watch c. 2 way speaker – suitable for sound reinforcement / Freq range suitable to be heard.

LINE ARRARY SPEAKER

3. Amplifier - Amplify audio signal. - Tone control available. - Power per channel not more than 100W - Input signal from CD have better distortion compare to the cassette i/p. MIXING AMPLIFIER/PUBLIC ADDRESS

Method of Power line distribution to the speakers Speaker selection based on : – - Sound strength - Speaker quantity - Low power amplifier – slow sound - High power amplifier – damage the speaker

For o/p amplifier low impedance; - total impedance value for all speakers should higher @ same value with the o/p amplifier Total o/p amplifier ≤ Combination of speaker impedance impedance For o/p amplifier high impedance ; - total power supplied to the speaker should be lower than the o/p amplifier capability. Total power supplied to speaker ≤ o/p amplifier

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Low Impedance Amplifier Amplifier produce full power o/p. The amplifer attached with speaker connection point that is labelled with ‘Com., 4Ω, 8Ω dan 16Ω’. Variety connection of the speaker method can be implement as long as the total impedance connected to the amplifier is suitable with the value of the amplifier terminal connection point.

16Ω 8Ω 4Ω Com.

8Ω 4Ω

4Ω

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High impedance amplifier Speaker installation method for this amplifier is called ‘Constant Voltage Distribution System’ (Sistem Agihan Voltan Tetap) The amplifer attached with speaker point that is labelled with ‘Com., 4Ω, 8Ω dan 16Ω’. All the speaker connection is in parallel via transformer for impedance matching. Voltage distribution value normally from 70V – 100V.

70V @ 100V line C

C

C

C

High impedance terminal

Low impedance terminal

C

C

Primary

Secondary

Type of the speakers & the range that will divide the speaker categories. High impedance Mark at the amplifier for high impedance connection  mark of 70V, 100V & 110V. Speaker condition For range more than 10 m. Every speaker is attached with MT. Horn type speaker.

Matching Transformer (MT) Attached with Horn Speaker type. MT will match power which was produced by amplifier with rating to Horn speaker. In other words, amplifier will induce MT and MT's output power to produce Horn speaker sound. This method can extend life time’s of the speaker.

Type of speakers & the range that will divide the speaker categories. Low impedance Mark at the amplifier for low impedance connection  Mark of 4Ω, 8Ω & 16Ω. Speaker condition that is categorized as high impedance connection  For range less than 10 m.  Speaker value – not same  Papercone & ceiling type speaker.

Speaker Selection 

Avoid non clearity problem and low power sound.

Class of Speaker 1. Open place - freq waveform between 800 Hz ~ 6000 Hz 2. Music background – for gentle music freq between 100 Hz ~ 800Hz 3. Music – refer to the hall condition/ design for music 40Hz ~15000Hz

Speaker Arrangement 1. Main System - Speaker place at the center of the hall to control sound convergence to one direction. Low maintenance cost. 2. Spreading System - Scattered arrangement for speakers. - Speaker combination can strengthen sound at the small space. - However the sound quality is reduce. 3. Combination System - Combination of 2 system.

Arrangement & Speaker power distribution at the internal building area.  When setting the location of speaker in a room, factor of level of noise, height of ceiling, wide area of the room, use of the speaker & etc.  Below shows the criteria taken on speaker installation :-

Speaker

Keluasan kawasan bagi memperolehi 76dB keluaran maksima

WT – 707N (7W)

Kira-kira 32m persegi

WT – 715N (15W)

Kira-kira 64m persegi

WT – 202AN (10W)

Kira-kira 80m persegi

WT – 200AN (15W)

Kira-kira 100m persegi

Introduction to the Sound Reinforcement system and the different with the PA system.

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Sound Reinforcement system is used to produce a high energy sound signal in a wider area. Suitable for musical & vocal while PA system is suitable for speech and lecture session. Additional equipment can increase the capability of PA system to be a sound reinforcement system.

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The different between PA system and Sound Reinforcement system.

PA System

Sound Reinforcement

Limited space for equipment.

Wide area for equipment

Level of sound spreading are not wider. Lower cost

Wider of level of sound spreading

Low level of power & equipment

High power and use many equipment.

consumption.

More expensive cost

Suitable for general broadcasting Suitable for music Have 1 output channel

Have 2 output channel

1 channel o/p connected to a numer of speaker

2 o/p channel which each o/p have 1 speaker

Determination of Speaker Location Speaker

PointB

Point A

Point C

SOUND SYSTEM FOR 300 PEOPLE 3 to 3 rca cable

DVD Player

Limiter

Equalizer

Canon jack to mono jack cable

2 to 2 rca plug

Speakon plug to speakon plug cable

Crossover

Microphone Mixer

Amplifier Speakon plug to speakon plug cable

Speakers

Amplifier Wireless Mic

Sub-woofer

AUDIO COMPRESSOR Audio compressor – to compress @ limitting audio signal range.  Automatically fixed the signal level before send it to tape for recording  The compress process – to allow high/ low sound to be adjusted. 

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Basic control system in the compressor for user :* I/P – Set i/p level * Treshold – set level as a reference before the compressor operate. * Ratio – Set ratio to the rise of dB at the signal below treshold level. i.e. : Set 4:1 – bila treshold level dicapai, hanya 1dB kenaikan pd o/p utk setiap 4dB kenaikan pd i/p signal.

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Attack – Time taken to act when the signal cross the treshold level.

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Decay – Time taken back to normal condition when the signal become below the treshold level.

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O/P - Set o/p level.

AUDIO COMPRESSOR Circuit Operation IC1 act as amplifier where the gain determine by the R1– resistor between Drain & Source FET 2N3819. R1, R2 & R3 determine FET V-I characteristic.  O/p circuit connected with the feed back circuit.  Attack and Decay controlled by R4 (1ms) and R5 (517ms) 

AUDIO COMPRESSOR Circuit Operation 

2 way switch – select compressor working condition –fix gain @ adjustable.

VR1 – adjustable gain R4, R5 & feedback connection – fixed gain  In this circuit, a 29dB change in the input signal level produces a 9dB change in the output. 

AUDIO MIXER Audio mixer is used to mix many type of i/p sound signal.  Normally there is 8 ~ 10 input.  Low freq., mid range freq. & high freq.  The gain for i/p signal can be controlled to follow needs of user @ to get any special effect. 

AUDIO GRAPHIC EQUALIZER  Problem encounter - copying video tapes is the deterioration in the sound quality.   To correct the sound signal to produce the o/p sound approx. near to the original sound. ( by correcting the freq response ) .  5 band equalizer design to connect 2 AV o/p component to produce freq response that can be controlled.

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The five controls each have a range of +/- 10dB at centre frequencies of 100Hz, 300Hz, 1KHz, 3KHz & 10KHz. The 3dB points on each band are at 1/2 and twice the centre frequencies. Thus, the 3dB points on the 100Hz control are at 50Hz and 200Hz.  With all controls at maximum the unit has a total gain of 15dB.  The unit will accept an input of up to about 1V RMS (3V pk-pk) before distortion occurs with all controls at maximum.

AUDIO GRAPHIC EQUALIZER Circuit operation

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I/p is buffered by the IC1, (non-inverting with gain) which the gain can be controlled by altering R1 & R4. For easier explaination, assume 5 frequency selective sections disappeared, as well as five of the control pots.  The wiper of the remaining pot is connected to ground via a 1K0 resistor. So, the gain is 10. So, if the 1k replaced back to the 5 band freq, it shows that the gain can be adjusted.

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This cct is using capacitor and inductor in series connection as an adjuster. Gyrator model cct is used to replace the inductor due to difficulty Refer to the cct, C2 - capacitor. Whereas, C3, R7 & R8 act as inductor. Value of C3 will determine the freq for each band. In the last IC3 will function as Unity Gain buffer. SW1 act as selector switch to select unit to be in equalizer mode or not.

SOUND PROCESSOR 

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Function to change & adjust the sound structure to produce the best sound o/p. The sound effect that can be produce by this processor is like echo (gema), surround (modulasi keliling) etc. Normally used in the computer and television application. * A rapid repetition of the same note, a rapid variation in the amplitude of a single note, or an alternation between two or more notesThis is more usually called vibrato.

Sound Delay Cct 

To delay the signal, which makes the sound are far away.

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Normally in surround decoder cct where the o/p will provide a passable rear channel signal.

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As example, IC M65830 is use.

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This IC need 5V supply. Whereas pin 11 & 12 need good separation between ground for analog and digital signal I/P

DELAY

+/ -

To O/P

Cap 68nF at pin 16 & 20 – to control modulation ( conversion of digital & analog) & demodulation. However the tolerance should not exceeds 5% to get good result.  I/P driver cct – to decrease the i/p value signal to avoid overload. The max value for this IC i/p is 1 Vrms.  This is because signal for CD player normally at 2.5 Vrms. So, by using the driver cct, the signal can be decrease. 