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Flashcards in Noise Deck (29):
1

Socioacusis

Permanent hearing loss from environmental noise

2

Presbycusis

Hearing loss from aging

3

How many ft/sec does sound travel through air at OF, sea level

1128 feet per second (770 miles per hour)

4

How many feet per second does sound travel in water

4700 feet per second

5

What frequency range can the human ear hear

20 to 20,000 Hertz

6

What is a decibel (dB)

The ratio of the level of sound in question compared to the smallest sound distinguishable to the human ear.

7

How many dB in the following noises:

Whisper
Human conversation
Vacuum Cleaner
Semi Truck
Jet engine at take off

Whisper - 5
Human conversation - 40
Vacuum Cleaner - 60
Semi Truck - 80
Jet engine at take off - 140

8

Permissible Exposure Limit (PEL) for noise

85 dB @ 8 hours

9

3 devices used to measure noise

Sound level meters
Octave level analyzer
Noise dosimeter

10

Sound Level Meters

Converts pressure waves in the air to an electronic signal and displays the SPL (sound pressure level)

11

Octave Level Analyzer

Used to test human hearing by emitting different frequency sound waves

12

Noise Dosimeter

Consists of a sound meter, integrator and indicator. Worn by an employee to measure sound exposure over a work shift

13

What is TTS

Temporary Threshold Shifts. Hearing losses which are recoverable after a period of time. The body usually gives warning signals such as tinnitus (ringing in ears)

14

Permanent Threshold Shifts

Permanent loss of hearing from daily exposure over a long period

15

Baffles

are designed to impede or alter the direction of noise, thus reducing the noise. Common at shooting ranges and freeways.

16

What is SPL

Sound Pressure Level. A logarithmic measure of the effective pressure of a sound relative to a reference value. Sound pressure level, denoted Lp and measured in dB, is defined by.

Frequency and Duration

17

Doubling of sound pressures results in an increase of ___ dB

3 dB (e.g. two 100dB speakers would make 103dB)

Sound does not have an additive effect

18

Definition of noise

"unwanted sound"

19

Inverse Square Law

Doubling of distance from a noise source results in a reduction of -6 dB

20

Leq

Equivalent continuous sound level. expresses the sound energy average over a period of time

21

Continuous sound
intermittent Sounds
Impulsive Sounds

Continuous - vary little over a period of time
intermittent - Emitted throughout relatively quiet periods
Impulsive - High Sound levels with very short durations

22

The statistical Model

uses statistics to describe the noise environment. Noise levels are sampled at a constant interval.

23

LDN

Day-Night average sound level

24

Sound insulation

use of structures and materials to reduce transmission of sound

25

Sound transmission class

STC - a rating system to sound insulation properties of partitions such as walls, floor, ceilings

26

STL

Sound transmission loss - measure of sound insulation provided by a structural configuration

27

Sound-absorption coefficient

Ability of a surface to absorb sound

28

NRC

Noise reduction coefficient - is a scalar representation of the amount of sound energy absorbed upon striking a particular surface

29

What is the MOST common type of noise measurement device used for initial inspections?

Sound Level Meter