# Ergonomics Problem - Got a minute?

An air compressor in a small automotive repair shop generates noise at a constant pressure of 2.5 Pascals regardless of its running speed. On the other hand, the pitch (frequency) of
the compressor noise varies with speed.

What is the SPL of the compressor noise? Assume that a second compressor which generates noise at 97 dB is installed next to the first compressor. What is the combined SPL of the compressors?

One mechanic works in the shop. Over an eight hour day, he spends two hours on paid breaks in the front office (dB level = 80 dB) and the rest of the time he spends in the shop (dB level = 90 dB). During that time, the first compressor runs 30% of the time and the second compressor runs 20% of the time. The two compressors rarely run at the same time, so this situation can be ignored. By OSHA guidelines, what is the noise dose to which this mechanic is exposed? Does it exceed the permissible noise exposure?

Testing reveals that the mechanic does not notice an increase in sound pressure level from 60 dB until the sound pressure level is increased to 64 dB. Based on this info, can the mechanic detect by hearing alone when the second compressor runs at the same time as the first compressor?

This sounds like an assignment question. I dont know what it has to do with ergonomics either.

dB is a logarithmic scale. Every 3dB increase in noise level, though barely perceptible, corresponds to a doubling of sound energy.

Dont know about OSHA, but in Oz it is 85dB(A). I use AS1269 to work this sort of thing out.

Assuming it is not an assignment question, just put a noise dosemeter in the shop.

I mean a noise dosemeter on the mechanic.

We are not a homework service. If you’re having a problem, read the book, study your notes, or talk to your teacher. This thread is closed.

bibliophage
moderator GQ