Noise Flashcards
Socioacusis
Permanent hearing loss from environmental noise
Presbycusis
Hearing loss from aging
How many ft/sec does sound travel through air at OF, sea level
1128 feet per second (770 miles per hour)
How many feet per second does sound travel in water
4700 feet per second
What frequency range can the human ear hear
20 to 20,000 Hertz
What is a decibel (dB)
The ratio of the level of sound in question compared to the smallest sound distinguishable to the human ear.
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
Permissible Exposure Limit (PEL) for noise
85 dB @ 8 hours
3 devices used to measure noise
Sound level meters
Octave level analyzer
Noise dosimeter
Sound Level Meters
Converts pressure waves in the air to an electronic signal and displays the SPL (sound pressure level)
Octave Level Analyzer
Used to test human hearing by emitting different frequency sound waves
Noise Dosimeter
Consists of a sound meter, integrator and indicator. Worn by an employee to measure sound exposure over a work shift
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)
Permanent Threshold Shifts
Permanent loss of hearing from daily exposure over a long period
Baffles
are designed to impede or alter the direction of noise, thus reducing the noise. Common at shooting ranges and freeways.
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
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
Definition of noise
“unwanted sound”
Inverse Square Law
Doubling of distance from a noise source results in a reduction of -6 dB
Leq
Equivalent continuous sound level. expresses the sound energy average over a period of time
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
The statistical Model
uses statistics to describe the noise environment. Noise levels are sampled at a constant interval.
LDN
Day-Night average sound level
Sound insulation
use of structures and materials to reduce transmission of sound
Sound transmission class
STC - a rating system to sound insulation properties of partitions such as walls, floor, ceilings
STL
Sound transmission loss - measure of sound insulation provided by a structural configuration
Sound-absorption coefficient
Ability of a surface to absorb sound
NRC
Noise reduction coefficient - is a scalar representation of the amount of sound energy absorbed upon striking a particular surface
What is the MOST common type of noise measurement device used for initial inspections?
Sound Level Meter
A ______ is a dimensionless unit to express physical intensity or sound pressure levels.
Choose one answer.
decibel
The unit of measurement most commonly used to measure loudness is called
phon
the most important aspect of noise is the __ and __ of the sound.
frequency and duration
who sets guidelines for noise regulation?
ACGIH- American Conference of Governmental Industrial Hygienist
who established title 8 noise exposure standard?
CalOSHA
CalOSHA Permissible Exposure Limit (PEL) of sound
85dB within a 8hr work shift
OSHA Permissible Exposure Limit (PEL) of sound
90dB within a 8hr work shift
