Lecture 15 Noise

Question 1

Frequency and wavelength

Answer 1

inverse relationship

Wavelength = constant / frequency

as frequency decreases, wavelength increases and vice versa

Question 2

Higher frequency =

Answer 2

-easier to absorb in sound control

Question 3

Sound pressure level

Answer 3

• can be measured with a noise meter
• Calibration: 1000 Hz

Question 4

How many Pascals is Ambient Air Pressure?

Answer 4

101.325 kPa

Question 5

Learning interference

Answer 5

-Aircraft noise
-train noise
-traffic and street noise

Question 6

Measuring Noise-Induced hearing loss (NIHL)

Answer 6

-Use a normal audiogram

Question 7

Hearing protection uses:

Answer 7

-When engineering controls can’t reduce noise enough
-For employees with noted hearing loss
-While engineering controls are being implemented

-Wear them all of the time not just sometimes

Question 8

Identifying the sources of noise and their importance

Answer 8

-Sound can be generated by: Vibrating surfaces, Mechanical impacts, Pulsating gas
flows, Air flow over surfaces, Compression & rarefaction of
medium

Question 9

Measuring conditions

Answer 9

– Obtain frequency spectrum
– Turn components on & off
– Conduct near‐field readings
– Plot frequency data to observe possible BPF, gear meshing,
etc.

Question 10

Prioritizing for Noise control

Answer 10

– Plot linear versus A‐weighted
– Rank noise order sources (dBA)
– Determine interrelationship between noise source
and receiver
– Consider benefit to employees in the area
– Consider Noise Criteria

Question 11

How does distance impact noise?

Answer 11

As you increase the distance away from the source, you will drop down in sound by the log (about 6 deceables dBA)