Important Questions with Answers

ANNA UNIVERSITY Part A '2' Marks Q & A

1. Enumerate the ways in which sound is classified

 Sound is classified on the basis of frequency

(i) Infrasonics (frequency less than 20 H_z)

(ii) Audible sound (frequency in between 20 Hz and 20,000 H_z)

(iii) Ultrasonics (frequency greater than 20 kH_z)

2. Define absorption co-efficient of a material. What is its unit?

The absorption co-efficient of a material is defined as the ratio of sound energy absorbed by it's surface to that of the total sound energy incident on the surface.

The unit of absorption co-efficient is open window uint(O.W.U).

3. What are the acoustical factors to be considered while we construct any buildings?

• Reverberation time

• Loudness

• Focussing

• Echoes

• Echelon effect

• Resonance

• Noises

4. Mention any four sound absorbing materials.

Carpets, glass, wool, hair, furniture also wood, foam materials, audience.

5. What is noise? How is it classified?

Unwanted sound reaching our ears is called the noise

There are three types of noises

• Inside noise

• Airborne noise

• Structure borne noise

6. What is inside noise? Give the remedy to avoid such noise.

The noises produced inside the same room are known as inside noises.

Remedy

• The machineries and any sound producing equipments may be placed over the sound absorbing materials or pad.

• This type of noises can also be reduced by covering the walls, floors and ceilings with suitable sound absorbing materials.

7. What is air borne noise? Mention the ways to avoid such noise.

Noise from outside through open windows, doors, ventilators is known as air-borne noise.

Remedy

• By allotting proper places for doors and windows.

• By making perfect arrangement for shutting the doors and windows.

• Using heavy glasses in doors, windows and ventilators.

• By making the hall air conditioned, this noise may be eliminated.

8. What is structure borne noise?

The noise through the structure of the building is called structure borne noise.

9. What are sound absorbing material?

The special materials used to increase the absorption of sound waves or to reduce the reflection of sound waves in a room or hall are known as sound absorbing materials.

10. What are the requirement of a good acoustical material.

• It should be durable and should not be liable to be attacked by insects, termites, etc.

• It should be easily available at a reasonable cost.

• It should be efficient over a wide range of frequencies.

• It should be fire resistant.

• It should give pleasing appearance after fixing.

• It should have high coefficient of absorption.

•  It should have sufficient structural strength.

11. What are the types of sound absorbing material?

(a) Porous absorbents

(b) Cavity resonators

(c) Resonant absorbing or panel absorbers

(d) Composite types of absorbents.

12. How are noises measured?

Noise meters

These are the instruments specially designed for noise measurement from low to high frequencies, characteristics of human ear capacity. Noise meters record the dB scale for routine measurement of general noise levels.

Refined noise meters have been developed to take care of peak noise levels, duration of noise exposure and quality of noise which are aspects of specified noise situation.

13. What is sound insulation and how is it measured?

The art of preventing the transmission of noise inside or outside the hall or rooms of a building is known as sound insulation.

It is also called sound proofing and it is a measure used to reduce the level of sound when it passes through the insulating building component. The basic principle of sound insulation is to suppress the noise.

The sound reduction index is used to measure the level of sound insulation provided by a structure such as a wall, window, door, or ventilator.

14. What are the main actions which causes impact of noise in multistoreyed buildings?

1. Speech privacy (will not be there)

2. Background noise (e.g fan, a.c, generator, printer)

3. Sound masking

4. Orientation of buildings

ANNA UNIVERSITY Part B (16 Marks) Questions

1. Explain the different types of sound absorbing materials.

2. Describe the methods of sound absorption.

3. Explain sound insulation measurement.

4. Write a note on noise measurement and the impact of noise in multi storeyed building.