Ch. 33 - Acoustics Flashcards
What is attenuation?
It means to reduce sound
What does IIC stand for?
Impact Insulation Class
What does the specific IIC number quantify?
The impact sound transmission rating of a ceiling or floor
What is the noise reduction coefficient?
The average sound absorption coefficient to the nearest 0.05. It is measured at the four octave band Frequencies 250, 500, 1000, 2000
What is an octave band?
A range of frequencies that is twice that of the lower
Define Sound Transmission Class or (STC)
A single number average over several frequency bands of a barriers ability to reduce sound. The higher the number the better the overall sound reduction.
_________ is the difference in decibels between the sound power incident on a barrier in a source room and the sound power radiated into the receiving room
Transmission Loss
In general transmission loss through a barrier tends to _______ with the frequency of the sound
Increase
A wall with a 0.1% opening from cracks, holes, etc) will have a maximum transmission loss of about how many decibels?
30db
A hairline crack will decrease a partitions transmission loss by about how many decibels?
6db
____________ opening in a 100 sq foot wall gyp. partition can transmit as much sound as the entire partition.
A 1 inch square opening
in a 100 sq foot wall gyp. partition can transmit as much sound as the entire partition.
T/F If A barrier with has an STC rating of 25, normal speech can be clearly heard through it
True
T/F If A barrier with has an STC rating of 30 Loud speech can NOT be heard and understood.
False, Loud speech can be clearly understood, but normal conversation would sound muffled.
What STC rating should the wall be at in order to absorb loud speech?
46-50, however loud noises can be faintly heard
What is the average absorption coefficient of a room?
0.20
