Noise and Vibration

Question 1

What are some engineering methods for reducing noise?

Answer 1

Control at the source, along the path, or at the ear. Dampeners, coverings, containers, sound shields/barriers, sound absorbing materials, PPE

Question 2

Why is noise bad?

Answer 2

• It can cause hearing loss.
• Affects performance and productivity
• Can be annoying
• Can interfere with spoken communication

Question 3

What kind of scale is the decibel measure?

Answer 3

Logarithmic scale

Question 4

What are the 2 main branches of ergonomics and the three underlying disciplines that ergonomics is based on

Answer 4

branches: Man as machine and Man as info processor. Disciplines: Anatomy, physiology, psychology

Question 5

How is ergonomics different from studying basic & medical sciences such as anthropology, cognitive science, psychology?

Answer 5

Because ergo is about designing around human behaviour, not to just understand

Question 6

What problems led to the invention of the “pilot’s control stick”

Answer 6

More pilots killed in training than war activities

Question 7

Provide 2 important emerging areas in ergonomics around the around from the 1996 International Ergonomics Association Survey.

Answer 7

Cognitive ergonomics and organizational issues (change management?)

Question 8

What are 5 things to consider when designing to make system safer

Answer 8

1 Task Allocation btwn man/machine. Hazards?

2 Poor posture conditions(comfort as well as convenience)

3 Ambient environment (light, noise, vibration, temp)

4 Organizational factors: allocation of responsibility, autonomy, comm. policies

5 Machine Design (better controls/display)

Question 9

According to Miles & Swift 1998, why is it not a good idea to “do ergonomics later”?

Answer 9

It costs a lot more to implement changes, even conceptually, at later stages in design process

Question 10

Provide 5 obstacles encountered by design and production engineers when trying to integrate ergonomics into their work

Answer 10

• No tradition for doing it
• Management not committed
• Not req’d by authority
• Lack of time
• Lack of ergo knowledge

Question 11

Explain/compare Conductive vs. Neural hearing loss

Answer 11

Conductive: Mechanical rupture of eardrum/bones in middle ear. Due to sudden intense pressure wave. May be partial loss, total temporary, or permanent

Neural: Through prolonged noise exposure, cause nerve damage
dep. on intens, frew, duration exposure

Question 12

Types of Sound Analyses? (2)

Answer 12

Octave Band: noise measured at each octave, divide audible range into 10 bands at certain freqs

Third octave band: one measure for every 3rd octave

Question 13

Describe 2 ways of measuring noise

Answer 13

Dosimeter: measures a workers daily dose. Summarizes noise over a day

Sound Level meter: Measures sound readings of noise produced by machines worker exposed to. Can be set to different freqs.

Question 14

Describe 5 costs occurring as a result of poor human factors considerations

Answer 14

• Reduced productivity
• absenteeism and sickness
• Reduced quality
• Reduced business Flexibility
• Hiring costs
• Training costs
• Cost of lost knowledge

Question 15

Why is it so difficult to come up with a theory relating noise and performance?

Answer 15

Many different types of noise and many different types of tasks make it difficult to peg a generally applicable theory. Noise: intermittent to continuous of all kinds.

Tasks: skill based, rule-based, knowledge based

Question 16

Name two types of hearing protection

Answer 16

Earbuds and earmuffs. (Cotton does nothing)

Question 17

Yerkes-Dodson’s law. What conclusions does the figure provide in terms of effect of noise on performance?

Answer 17

Some noise can be good, with diminishing returns up to an optimum performance at which point more noise becomes a bad thing. The optimum level is different fro skill vs. task based work

Question 18

What are Preferred Noise Criteria (PNC) Curves?

Answer 18

The curves tell you, based on measurements, how good the conditions are for listening/verbal communication.

The lines show that lower frequency sounds can occur at higher volumes than higher freq sounds, and be at the same listening level.

Question 19

How does the PSIL (Preffered speech interference level) work?

Answer 19

Value taken by avg’ing decibel evels of bands at 500, 1000, 2000Hz. Good approx when real noise situation isnt wide spectrum

Knowing the distance btwn people, and the avg decibel value, one determines what level of effort would be required from a speaker for the other to hear them. (Throat stress)

Question 20

What are the 2 kinds of vibration that cause health hazard?

Answer 20

Whole Body Vibration- As transmitted through a seat

Hand Vibration- As from using power tools

Question 21

Why does vibration cause discomfort?

Answer 21

Diff body parts have different resonant frequencies

Question 22

What are physiological effects of vibration exposure?

Answer 22

Increased heart rate, reduced visual acuity, incr. blood pressure

Question 23

What are Reynauds disease and Darts disease?

Answer 23

Reynauds: as a result of 50-500Hz hand vibration, fingers become white. Nerves and blood vessels are permanently damaged. Stiffness and numbness, gradual loss of muscle control. Accelerated by cold weather and smoking

Darts disease: Less common, occurs at around 100Hz. Blood pools in hands. They swell and become blue. Painful. Use vibration attenuating handle to avoid (mere softness wont do much)