UNIT 4- Onemarks-Eng 1 Prot

24042--Communication engineering Unit-IV

UNIT 4-AUDIO SYSTEMS

1. State Acoustic principle.

The study about the changes in the sound waves are said to be acoustic. In acoustical system, the oscillations in sound

pressure are picked up by some form of receiving electro acoustic transducer called microphones.

2. What is a microphone? Give its types.

Microphones are used for converting sound signals into electrical signals. It is operated only in air.

Two types: 1. Pressure microphones 2. Pressure gradient microphones

3. What is a pressure microphone? Give examples.

In pressure microphones, the acoustic (SOUND) pressure acts only one side of the moving element (DIAPHRAGM) &

the resulting output is proportional to the pressure applied to the moving element.

Example: 1. carbon microphone 2.Condenser microphone 3.Piezoelectric microphone 4.Moving coil microphone

4. What is a pressure gradient microphone? Give examples.

In pressure gradient microphones, the acoustic pressure (SOUND) acts on two sides of the moving

element(DIAPHRAGM) & the resulting output is proportional to the difference between the pressure acting on the two

sides of the moving element. Example: Velocity ribbon microphone.

5. What are the advantages & disadvantages of carbon microphone?

Advantages: 1.Electrical output is high 2.low cost 3.It is robust.

Disadvantages: 1.Frequency response is poor 2.Hissing sound is produced.

6. What is the application of carbon microphone?

It is widely used in telephone & radio communication.

7. What are the advantages & disadvantages of condenser microphone?

Advantages: 1. low distortion 2.small in size 3.high signal to noise ratio.

Disadvantages: high internal impedance requires voltage ranging from 200 to 400 volts.

8. What is the application of condenser microphone?

It is used in acoustic research for standard calibration purpose & for high fidelity recording of sound.

9. What are the advantages & disadvantages of piezoelectric microphone?

Advantages: 1. high sensitivity 2.small size 3.low cost 4.frequency response is good

Disadvantages: not suitable for hot climates as the crystal loses the piezoelectric properties.

10. What is the application of piezoelectric microphone?

It is used in public address system (Public meetings) & for hearing aids.

11. What are the advantages of moving coil microphones?

1. Light weight 2. Requires no external voltage 3. Internal impedance is low

12. What is velocity ribbon microphone?

It works on the principle of pressure gradient which implies the electrical signal produced is proportional to the

difference in pressures acting on its two sides of moving element.

13. What is the use of velocity ribbon microphone?

It is used particularly in studio work.

14. What are the advantages & disadvantages of velocity ribbon microphone?

Advantage: Response curve is better than moving coil type.

Disadvantage: It requires a built in type transformer, its internal impedance is low.

~~All The Best~~ Sukesh.R Lec/ ECE, GRG Polytechnic College, CBE-107.


15. Compare carbon microphone & condenser microphone.

S.No. Carbon Microphone Condenser Microphone

1 Stiffness Controlled System Mass Controlled System

2 High Electrical Output Low Electrical Output

3Operation depends upon variation of resistance of carbon button

Operation depends upon variation of Capacitance of a capacitor

16. Compare condenser microphone & piezoelectric microphone.

S.No. Piezo Electric Microphone Condenser Microphone

1 Stiffness Controlled System Mass Controlled System

2 High Electrical Output Low Electrical Output

3 Operation depends upon piezoelectric effectOperation depends upon variation of Capacitance of a capacitor

17. Define loudspeaker.

Loudspeaker is an electro acoustic transducer, which converts electrical signal into sound signal.

18. What are the characteristics of loudspeaker?

1. Efficiency approaches 100 percent 2. Harmonic & inter modulations not present

3. Input signal are produced faithfully

19. What are the types of loudspeaker?

1. Dynamic cone type moving coil loud speaker 2. Horn Type moving coil loudspeaker

3. Electrostatic type loudspeaker

20. What are the advantages & disadvantages of dynamic cone type loudspeaker?

Advantage: 1. Compact in size 2. Low cost 3. Better response in audio range

Disadvantage: 1. Low efficiency 2. low power 3. narrow directivity

21. What is the application of dynamic cone type loudspeaker?

It is used in all audio systems

22. What are the advantages of horn type loudspeaker?

1. Sound effect of this speaker is very high & efficient 2. Diaphragm is smaller in size

Power handling capacity is more than 100 watts.

23. What is the use of electrostatic type loudspeaker?

This type of loud speakers used in high fidelity applications

24. Compare cone type & horn type loudspeaker

S.No. Cone Type LS Horn Type LS1 Sound effect of this speaker is less Sound effect is very high & efficient2 Diaphragm size is large Diaphragm size is small

3Power handling capacity is from few milli watts to several 100 watts

Power handling capacity is more than 100 watts



25. Give the speaker specifications.

1. Diameter of the speaker 2. frame Type 3. Wattage rating 4.Voice coil impedance

26. Compare woofer & tweeter

S.No. Woofer Tweeter

1It is used for the reproduction of low frequencies

It is used for the production of high frequencies

2 It has large diameter cone It has small diameter cone3 High wattage rating , High cone depth low wattage rating , Low cone depth

27. Define cross over network.

To improve the quality & performance of amplifiers & radio receivers, various control circuits are used. These circuits

are called cross over networks.

28. What is Woofer, Mid-range (Squawker), Tweeter? & Draw the frequency response curve.

Woofer- It used to reproduce Low frequencies

Squawker – It used to reproduce mid-range frequencies

Tweeter – It used to reproduce high frequencies

29. What is surround sound system?

Multichannel audio technique is used for enriching the quality of sound reproduction of a recorded source. It is for 3D

sphere of human hearing achieved with audio channels.

30. What is CD? Mention its layers.

CD- Compact Disc- it could store wide variety of data formats like text picture, video, software etc. It is 12cm or

5inch in diameter. It has three layers: Transparent layer , thin metallic layer, outer layer of protective acrylic.

31. What are the advantages of CD?

1. High signal noise ratio 2. Small size 3. low distortion 4. Excellent Frequency range

32. What is MP3? What is MPEG?

MP3 - MPEG-1 Audio Layer 3 : is commonly referred to as MP3. It is a digital encoding format using a form of lossy

data compression.

MPEG stands for M oving P icture E xperts G roup . It is for compressing moving picture. It is an audio\ specific format.

33. What is DVD?

DVD:- D igital V ersatile D isc [OR] Digital Video Disc - could store wide variety of data formats like picture, audio,

video, software etc. It needs manufacturing precision because of very fine encoding & extremely small track thickness.

34. Define stereophonic system.

A stereophonic system is a two channel system of sound recording & reproduction, which gives the feeling of depth &

direction to the reproduced sound like 3D audio.

35. What is Hi-Fi system?

Hi- Fi:- High Fidelity. When the sound reproduced with a degree of similarity to the original or live sound, it can be

said to be of high fidelity or simply Hi-Fi.

36. What are the characteristics of Hi-Fi system principles?

Signal to noise ratio should be finite No frequency distortion

No non linear distortion No spatial distortion

37. Expand DTS

Digital Theater System OR Digital Track Sound



38. What is DTS?

DTS is a series of multichannel digitalized audio technologies.

39. What is bit rate?

The bit rate is used to specify how many kilobits the file may use per second of audio as in when ripping a CD to MP3

format.

40. State the frequency bands of Dolby A system.

Band 1 – below 80Hz

Band 2 – 80Hz to 2999Hz

Band 3 – 3000Hz and above

Band 4 – 9000Hz and above

41. How the Surround sound is produced?

1. Microphone technique 2. Psycho acoustic sound localization 3. Huygens principle

Part B1. Explain carbon microphone with neat diagram (6 MARKS)2. Explain condenser microphone with neat diagram (6 MARKS)3. Explain piezo-electric microphone with neat diagram (6 MARKS)4. Explain moving coil microphone with neat diagram (12 MARKS)5. Explain velocity ribbon microphone with neat diagram (12 MARKS)6. Explain dynamic cone type moving coil loud speaker with neat diagram (12 MARKS)7. Explain Horn type moving coil loud speaker with neat diagram (12 MARKS)8. Explain Electrostatic type loud speaker. (6 MARKS)9. Explain 3 Way cross over network. (12 MARKS)10.Explain Surround sound system with neat sketches. (12 MARKS)11. Explain CD recording and reproduction (12 MARKS)12. Explain MP3 system (6 MARKS)13. Explain DVD system (6 MARKS)14. Explain Stereophonic system (6 MARKS)15. Explain Hi-Fi system (6 MARKS)16. Explain DTS. (6 MARKS)


http://en.wikipedia.org/wiki/Surround_sound

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UNIT 4- Onemarks-Eng 1 Prot