Department of Engineering
BACHELOR OF SCIENCE IN CIVIL ENGINEERING
ENGINEERING UTILITIES 2
STUDY QUESTION CHAP. 23-24
Alfred V. Matnog 01-21-2021
BSCE-3A
CHAPTER 23
1. What is sound?
Ans.
Sound is defined as a rapidly varying pressure wave within a fluid medium such as air or
water that is capable of being detected by the human ear. Sound is produced when the air is
disturbed in some way (e.g., by speaking, by clapping hands, or by a vibrating object).
2. What units are used to identify the intensity of sound?
Ans.
The decibel (dB) is a measure of the intensity of sound. The decibel scale runs from the
faintest sound the human ear can detect, which is labeled 0 dB. A bel is another unit for comparing
intensities of sound: 1 bel equals 10 decibels. The A-weighted decibel (dBA) is a measure of sound
intensity level that is adjusted to match the acuity of the human ear, which does not respond
equally to all sound frequencies.
3. What is the difference between sound and noise?
Ans.
Sound moves in a straight-line path unless it is interrupted. When sound waves strike an
object, they can be reflected, absorbed, or transmitted. While noise is any disagreeable or
undesirable sound that interferes with rest, sleep, mental concentration, or speech
communication. Simply, noise is sound that is not part of what a person is trying to hear.
4. What is sound transmission?
Ans.
Sound may be transmitted through the air or through the structure. Planning is required
to reduce the transmission of sound from the exterior to the interior and from room to room.
Basically. in each space it is necessary to keep the necessary sounds in and undesirable sounds
out.
5. What is the difference between airborne sound and structure-bone sound?
Ans.
Airborne sound is transmitted through air or gas as a medium rather than a liquid or solid.
Structure-borne sound is transmitted through a construction assembly (e.g., wall, floor, and
ceiling).
, 6. If the sound level changes from 42 to 45 dBA. how noticeable would it be to a person in the same
room? What if the sound level changes from 42 to 62 dBA?
Ans.
When a new noise source similar to the existing noise sources generates an increase in
noise of 5 dBA or more, the increase would be noticeable where the ambient level is less than 60
dBA. Where the ambient level is between 60 and 65 dBA, an increase in noise of 3 dBA or more
would be noticeable, and an increase of 1.5 dBA or more would be noticeable where the ambient
noise level exceeds 65 dBA.
7. What is the STC?
Ans.
The sound transmission class (STC) is a single-number rating system that rates the ability
of a wall or other construction to block sound transmission. It is used to compare the airborne
sound-isolating characteristics of construction assemblies used to separate occupied spaces.
8. What is the IIC?
Ans.
The impact insulation class (IIC) is a number rating, based on standardized test
performance, for evaluating the effectiveness of assemblies in isolating impact sound
transmission. The IIC is the current rating system used to rate the ability of floor ceiling assemblies
to resist the transmission of impact sound.
9. What is the NRC?
Ans.
The noise reduction coefficient (NRC) is also used to measure the ability of a material to
absorb sound rather than reflect it. The material absorbs part of the sound striking the surface of
the material and part of it is transmitted through to the other side of the material.
10. How can the surrounding environment affect sound control?
Ans.
Quite frequently, the site itself and the project being de-signed necessitate that the quiet
areas must be located adjacent to a noise source. Noise can be reduced by placing solid walls on
the side of the building facing the noise source and placing the windows on the side facing quieter
areas.
11. What methods might be used to control and isolate vibration noises in buildings?
Ans.
Noise can be reduced by placing solid walls on the side of the building facing the noise
source and placing the windows on the side facing quieter areas. Still, the designer must be careful
that, in placement of windows, doors, and other openings, noise does not enter through the
windows by bouncing off an adjacent wall.
BACHELOR OF SCIENCE IN CIVIL ENGINEERING
ENGINEERING UTILITIES 2
STUDY QUESTION CHAP. 23-24
Alfred V. Matnog 01-21-2021
BSCE-3A
CHAPTER 23
1. What is sound?
Ans.
Sound is defined as a rapidly varying pressure wave within a fluid medium such as air or
water that is capable of being detected by the human ear. Sound is produced when the air is
disturbed in some way (e.g., by speaking, by clapping hands, or by a vibrating object).
2. What units are used to identify the intensity of sound?
Ans.
The decibel (dB) is a measure of the intensity of sound. The decibel scale runs from the
faintest sound the human ear can detect, which is labeled 0 dB. A bel is another unit for comparing
intensities of sound: 1 bel equals 10 decibels. The A-weighted decibel (dBA) is a measure of sound
intensity level that is adjusted to match the acuity of the human ear, which does not respond
equally to all sound frequencies.
3. What is the difference between sound and noise?
Ans.
Sound moves in a straight-line path unless it is interrupted. When sound waves strike an
object, they can be reflected, absorbed, or transmitted. While noise is any disagreeable or
undesirable sound that interferes with rest, sleep, mental concentration, or speech
communication. Simply, noise is sound that is not part of what a person is trying to hear.
4. What is sound transmission?
Ans.
Sound may be transmitted through the air or through the structure. Planning is required
to reduce the transmission of sound from the exterior to the interior and from room to room.
Basically. in each space it is necessary to keep the necessary sounds in and undesirable sounds
out.
5. What is the difference between airborne sound and structure-bone sound?
Ans.
Airborne sound is transmitted through air or gas as a medium rather than a liquid or solid.
Structure-borne sound is transmitted through a construction assembly (e.g., wall, floor, and
ceiling).
, 6. If the sound level changes from 42 to 45 dBA. how noticeable would it be to a person in the same
room? What if the sound level changes from 42 to 62 dBA?
Ans.
When a new noise source similar to the existing noise sources generates an increase in
noise of 5 dBA or more, the increase would be noticeable where the ambient level is less than 60
dBA. Where the ambient level is between 60 and 65 dBA, an increase in noise of 3 dBA or more
would be noticeable, and an increase of 1.5 dBA or more would be noticeable where the ambient
noise level exceeds 65 dBA.
7. What is the STC?
Ans.
The sound transmission class (STC) is a single-number rating system that rates the ability
of a wall or other construction to block sound transmission. It is used to compare the airborne
sound-isolating characteristics of construction assemblies used to separate occupied spaces.
8. What is the IIC?
Ans.
The impact insulation class (IIC) is a number rating, based on standardized test
performance, for evaluating the effectiveness of assemblies in isolating impact sound
transmission. The IIC is the current rating system used to rate the ability of floor ceiling assemblies
to resist the transmission of impact sound.
9. What is the NRC?
Ans.
The noise reduction coefficient (NRC) is also used to measure the ability of a material to
absorb sound rather than reflect it. The material absorbs part of the sound striking the surface of
the material and part of it is transmitted through to the other side of the material.
10. How can the surrounding environment affect sound control?
Ans.
Quite frequently, the site itself and the project being de-signed necessitate that the quiet
areas must be located adjacent to a noise source. Noise can be reduced by placing solid walls on
the side of the building facing the noise source and placing the windows on the side facing quieter
areas.
11. What methods might be used to control and isolate vibration noises in buildings?
Ans.
Noise can be reduced by placing solid walls on the side of the building facing the noise
source and placing the windows on the side facing quieter areas. Still, the designer must be careful
that, in placement of windows, doors, and other openings, noise does not enter through the
windows by bouncing off an adjacent wall.
