Checklist Items Under Test: 6.24: Measure at each location on the test plan a nominal operating level of 65dB SPL (Sound Pressure Level) for conference speech, 60dB SPL for program material, A-weighted at all listeners’ ears ±2dB to maintain Uniformity of Coverage in the space (or at least 15dB above the ambient noise), with the control system volume control indicating “normal” or default setting. Record results for each channel and source.
Reasoning: Determining how loud a system should be is an often overlooked system performance specification. However, consistent default system levels across all rooms are a strong sign of well-integrated systems. Setting appropriate system levels is also important to avoid disrupting adjacent spaces. It also avoids grossly oversizing amplifiers. Ultimately, the default level should be determined by the client. However, as installers and designers, we should have a good understanding of realistic system levels to help guide their recommendations.
The Story: Many parties I’ve attended featured contested debates, while sipping a cool beverage, over how loud conference room systems should be. (What? What do you talk about when out at the discotheque?) Some say the system should be set to 80dBA, and the client can lower the volume if need be. Some say just slightly louder than conversation levels is more than adequate. Don’t get me started on the difference between program and speech levels! Should the program audio be set to “blow away” the client, or should it be set so speech in the room can still be understood over it while material is playing in the background? As are all things audio, “It depends.”
Typically, the answer is based on the particular client and the needs of the room. However, most clients are not comfortable speaking in terms of “dBs.” I find that the easiest thing to do is to take clients into an existing, equipped space, hand them the volume control, and ask them to adjust the speech and program levels to where they would like them to be. Then, I take my handy-dandy SPL meter and simply note the levels. The exercise takes all of five seconds, and now I know exactly how loud their rooms should be nominally.
Not only that, if I include those levels in the client’s performance specification, they can be applied globally, regardless of integrator or designer. This means that, no matter what country users are in, whenever they enter a conference room based on those specifications, the levels heard will be consistent. New York, Tokyo, London or Mechanicsburg: They’ll all have the same acoustical levels for their conferences. I think that’s pretty cool.
Let’s talk about the actual levels, though. The IEC 60268-16 standard specifies a sound pressure level for a standard talker to be 60dBA, measured at a distance of 1 meter. Stated a different way, the IEC says that if you are talking with a buddy and standing about three feet away, they will probably measure about 60dBA. This is a very useful reference point.
In a typical conference room, how loud do you think the system should be? Should the speech and conference levels in the room be heard at conversational levels? Or should they be slightly louder to keep someone’s attention? They probably shouldn’t be crazy loud like a movie theater (80dBA); that would be annoying to listen to and would disturb adjacent spaces around the conference room with bleed-through audio. Having done the exercise where the clients pick their favorite level with the volume control, many times, more often than not, they put the speech levels at about 65dBA. It’s slightly louder than a friendly conversation, but not too loud to be obnoxious. It’s also the level I recommend when one is not specified, or the client does not want to take responsibility for picking one.
Program material in conference rooms should be roughly the same level, in my humble opinion. We aren’t talking about home theaters or movie theaters. We are talking about commercial conference spaces. It might be totes dope to have a system that can produce 100dB SPL levels (and slightly dangerous) but, in reality, people are going to want to be able to interject comments over the program material. If the space is a screening room or hangout area, the needs will be different. However, most of my clients prefer the default program levels to be around 60dBA, or at conversation levels. It is comfortable to listen to, does not disrupt the adjacent spaces and, if you need to say something, you can still be heard without shouting.
I’ve seen many design packages calling for nominal levels of 80dBA, with 20dB of headroom. This is nonsense because no commercial client would allow that in their space. It’s simply too loud. However, it’s also very expensive to plan for. Let’s say, to drive my loudspeakers at 65dBA nominally with 15dB of headroom (to be able to produce 80dBA in the room without distortion), I need a 10W amplifier. With the same loudspeakers and room, I would need a 1000W+ amplifier to produce 100dBA in the room. Every additional 3dB requires double the amplifier needed. To get an additional 20dB, I need to double my amplifier size 7x. So, to meet that 80dBA with 20dB of headroom, I would have to install a ridiculous amplifier. It’s a waste of money, space and resources…especially when you know the users are only going to use 1% of that amplifier’s capacity to drive their system.
It’s always good to put a number on things. It separates the professionals from the practitioners. However, it’s even better when those numbers make sense. I use the standard talker level (60dBA @ 1m) as a reference every time I start addressing levels. It keeps things meaningful and realistic.