Ch. 14 Acoustics Flashcards
What are the three basic qualities of Sound
Velocity frequency and power
This quality of sound depends on the medium in which the sound is traveling in the temperature of the medium.
Velocity
This quality of sound is the number of cycles composed per second and is measured in hertz one hertz equals one cycle per second
Frequency
The quality of acoustic energy as measured in whites. This is what people perceive as loud Ness
Power
What is the threshold of human hearing and the threshold of pain
0 dB and 130 dB
What is the sound range of a healthy young person
It can range from 20 to 20,000 Hz and is most sensitive to frequencies in 3000 to 4000 Hz range
What range of sounds is speech composed of
Speech is composed of sounds primarily in the range of 120 to 8000 Hz, with most in the range of 200 to 5000
unwanted sound
Noise
What are the two basic problems controlling noise
Preventing or minimizing the transmission of sound from one space to another and reducing the noise within a space
What are the two important concepts in noise reduction
Transmission loss and noise reduction between two spaces
Takes into account only the loss through the partition
Transmission loss
This is dependent not only on the transmission laws but also on the area of the partition separating the two spaces in the absorption of the surface in the quiet room
Noise reduction
How to noise reduction be Increased
Increasing the transmission loss of the partition, by increasing the absorption in the quiet room, by decreasing the area of the common wall between the rooms or some combination of all three
The selection of wall construction in other building components, it’s single rating called what is often used to write the transmission loss of construction
Sound transmission class STC
The higher the STC rating, the better the barrier is in what
Stopping sound
This can be used to specify the maximum amount of continuous background noise allowable in a space, to establish a minimum amount of noise desired to help mask sounds, and to evaluate an existing condition
Noise criteria curve
This is used to control unwanted sound reflection, improve speech privacy, and decrease or increase reverberation
Sound absorption 
The ratio of sound intensity absorbed by the material to the total intensity reaching the material. The maximum therefore is one
The coefficient of absorption
What material is considered to be reflective what is it coefficient
0.2 or below
The average of the materials absorption coefficient see is at the four frequencies of 250, 500, 1000, and 2000 Hz, rounded to the nearest multiple of 0.05.
Noise reduction coefficient NRC
What is the NRC been superseded by
That sound absorption average SAA
The average of the absorption coefficients is for 12 1/3 octave bands from 200 Hz to 2500 Hz when tested in the same accordance with the a STMC423
S AA
What are some of the rules and her designers can follow for noise reduction in critical situation
Avoid designing rooms with hard, reflective surfaces on the walls, floor, and ceiling. The space will be to live and noisy.
The average absorption go fission of a room should be at least 0.2. An average absorption above 0.5 is usually not desirable, nor is it economically justified. A lower value for suitable for large Rams well larger values are suitable for small or noisy rooms
Each doubling of the amount of absorption in a room results in a noise reduction of only 3 dB hardly noticeable. To make any difference the total absorption must be increased by at least three times to change the reduction by 5 dB which is actually noticeable
Although it’s sort of materials can we please anywhere, ceiling treatment for sound absorption is Matt more effective in large rooms, while while treatment is more effective in small rooms 
What are the three primary ways sound can be controlled within a space
Reducing the level of loudness of the sound source, modifying the absorption in the space, introducing nonintrusive background sound to mask the unwanted sound
Are used to purposely introduce carefully controlled sound into space rather than rely only on random background noise
White noise, random noise, or acoustic perfume
what is one way to build a sound resistant partition
Add mass to the wall
What is the second technique to build a sound resistant partition
A Play insulation within the stud cavity. This at the words sound and reduces energy that is transmitted through one layer of the wall before it reaches the other.
What is the third way to build a sound resistant partition
Resilient channel can be used as furring strips on one side of the partition. Because of their design, only one leg of the channel touches the studs in the wall board floats and damp and sound striping it rather than transmitting it to the stud
What are ways to deal with doors placed in otherwise well-built sound wall
The perimeter could be completely sealed with weatherstripping specifically designed to sound ceiling at the GM and head to the threshold or automatic door bottom at the sill.
A piece of hardware that drops the seal from the door to the floor or threshold as the door closes. The door itself should be easy heavy as possible, preferably a solid forward door. Often, two doors are used, separated by small air gap
Automatic door bottom
How is glass soundproof
Interior glass lights can be designed with laminated glass set an a resilient frame. Laminated glass provides more mass, and the plastic innermost layer improves the dampening characteristics of the barrier. If additional transmission loss is required, two or more layers can be installed with an air gap between them
A condition in which talking may be hard as a general backgrounds down but not easily understood
Speech privacy
The divider should have a combination of absorptive services to minimize sound reflections over a solid linear called a what
Septum
Sound resulted in direct contact of an object with sound barrier, can occur on any surface, but it generally occurs on the floor and ceiling assembly. It is usually caused by foot fall, shuffle furniture, and dropped objects.
Impact noise
Impact noise is quantified by this it is a number, a single number rating of a floor/ceilings impact sound performance. The higher the better the floor performs in reducing impact sounds
Impact insulation class i I c
This is a single number rating of the average sound absorption of material over a limited frequency range, including 250 Hz, 500 Hz, 1000 hearts, and 2000 hearts, rounded to the nearest multiple of 0.05. These readings can range from zero to one. Acoustical ceiling tiles are generally in a range of 0.65 to 0.9. And open offices, values of 0.85 or higher are recommended
Noise reduction coefficient in RC
This is also a single number rating, but the frequency range includes 500 Hz, 1000 Hz of a 2000 Hz, and 4000 hearts, this range more closely represents the frequencies of speech and may be a better rating to use in evaluating in selecting ceiling tiles
Speech range absorption SRA
A single number measure of a transmission loss through ceiling tiles between two closed rooms where there’s no war other barrier above the suspended ceiling. It gives in a given in units of decibels and is similar to the STC values described in the previous section. Most acoustical ceiling tiles have a rating between 30 to 35 dB which is minimally effective at blocking sound.
Ceiling attenuation class CAC
The two methods used to measure speech privacy and open offices
Articulation class and articulation index
A single member summation of how effective is ceiling is in absorbing sound reaching out from overload partitions. The rating is a summation of waited sound attenuation is in 15 test in frequencies from 200 Hz to 5000 Hz, with higher waited factors in the frequencies representing most human speech. The test is used to determine this writing uses a 9 foot high ceiling and standard 60 inch high partitions
Articulation class AC
Measures the performance of all elements of a particular configuration working together, including ceiling absorption, space to voters, furniture, light fixtures, partitions, background masking systems are white noise, HVAC system sound. Does predicts the intelligibility of speech for a group of talkers and listeners. The best results of the test is a single number writing, which is a range of zero to one with 0 being completely private and one thing absolutely no privacy.
Articulation index AI
