dB meter

[museav]

This topic comes up often in other forums and it is alwasy noted that things such as how and where you make the measurement potentially make a significant difference in the results. With the same output at the speaker or even the nearest listeners, a person measuring dBA, slow response at a back corner of the house or at a booth in a room with poor coverage could get a reading 20dB or more lower than someone measuring dBC, fast response in the middle of the house. The relationship of the peak and average levels and which are being reported can also have a significant bearing on the numbers. So can the frequency content, using dBSPL A-weighted can allow for much higher low frequency levels without affecting the actual measurement although there may be a noticeable difference in the perceived level. And of course the application and intended audience can dramatically affect what is considered acceptable. So comparing to any numbers other may use is most useful when as many of these factors are known as possible.

 

[seanandkate]

figure out what "decibel" level is comfortable to you and the staff or management of the specific production, then monitor levels throughout the performance to make sure it doesn't exceed that level on the meter.

Ay, there's the rub! Trying to get a consensus in a staff of 100 is like herding cats. Maybe I'm asking the wrong question. How about "What is the level beyond which it becomes unsafe for someone to listen for a prolonged period of time?" Does that help at all?

When someone comes to me and says' "It's too loud", me replying that it's not to loud for me doesn't relly put the issue to rest. If I could say, "This level is standard" or "120 dB is what safety expert say is unsafe. We're at 105" that might not make it less loud for them, but it hopefully ends the conversation.

 

[derekleffew]

See Decibel (Loudness) Comparison Chart. It says right there "Loud rock concert...115dB." Unfortunately, makes no mention of how or where the reading is taken or weighted.

 

[seanandkate]

See Decibel (Loudness) Comparison Chart. It says right there "Loud rock concert...115dB." Unfortunately, makes no mention of how or where the reading is taken or weighted.

Thanks Derek. Do you suppose the 90-95 dB level they say is the "Level at which sustained exposure may result in hearing loss," is talking about somebody pulling an 8 hour shift somewhere, as opposed to a short term event?

Whoops--I withdraw the question. Should have scrolled down more!

 

[museav]

Actually, you were right to ask the question and they are wrong to present it as they did. OSHA uses an 8 hour dose, what they are showing in that chart are the exchanges, for example 105dBA for one hour equates to a full dose, the rest of the 8 hour period being used must then have sound levels sufficiently low to not further add to the dose received.

Another issue is that OSHA relates to hearing conservation and employer action and not directly to hearing loss. Nothing in OSHA relates to controlling the source levels, it all relates to when employers have to initiate various hearing conservation processes. That could be reducing the source levels but it could also be limiting exposure, providing hearing protection, periodic audiometric testing, etc.

I could go on but the point is that the OSHA chart as shown on the site is presented completely out of context and too often shows someone who doesn't really understand the subject.