I'm sure this will come up,and I've researched this in the past, but what type of meter do you purchase, and how about those cool smart phone apps?
Here is an Amazon link to a dosimeter that I have researched and own for safety program noise level testing. I use the Extech 407730, and it costs about $70.
http://amzn.to/1k2bGgQ .
This is a great tool for you course to have. And it's specifically designed for measuring noise levels so that you can maintain safe worker sound level exposures. It is also an ANSI Type 2 compliant device.
I have researched iPhone dosimeter applications (phone app's), and my recommendation is to not use this app, or any other smart phone app, for sound level safety compliance for a number of reasons.
Variability in microphone performance, microphone noise limit maximum dB levels of smartphone microphones (100-105 dB on average), different microphone types on different phone, etc, just to name a few.
I have downloaded the SoundMeter+ onto my iPad. It's a fun phone app for informational purposes, and general reference only. The Soundmeter+ literature clearly states that their smartphone application is IEC 61672 and OSHA compliant. Upon further reading within their app description they also say "This app and all its information are not intended to be used as legal evidence for workplace/merchandise safety, or for any other fields."
Another phone sound meter app for smartphones offers this information - "REMEMBER!! The smart phone microphones were aligned to human voice (300-3400Hz, 40-60dB). Therefore the maximum values are LIMITED by the manufacturers. The very loud sound(100+db) cannot be recognized. Moto Droid(max.100), Galaxy S3(81dB), Galaxy Note(91dB), Galaxy S2(98dB)"
Another phone sound meter app site clearly states that "Obviously, there was never an expectation that the iPhone's inexpensive microphones would perform in a manner consistent with precision measurement mics that are (justifiably) much more expensive."
For the safety of you, and your employees, I recommend you get a scientific tool that was designed specifically for measuring sound accurately such as the Extech 407730. I have one that I use, and its easy to operate, works perfectly, and is ANSI 2 compliant. You can use other ones...this is just on that I researched before buying, and know it works great.
Extech 407730 -
http://amzn.to/1k2bGgQOSHA ANSI 2 Compliant Device -
https://www.osha.gov/dts/osta/otm/noise/exposure/instrumentation.html