The Qualiverse - Audio Test Plan
Can you hear me now?
Do you guys remember that Verizon guy? He’d walk around the US on his cell phone asking, “Can you hear me now? Good. *Take a few steps* Can you hear me now? Good!” His character’s name was literally “Test Man”. Paul Marcarelli was a phenom with that one character and that one line. He’s now worth over $10M and has not only worked for Verizon, but also for Old Navy, Merrill Lynch, Dasani, T-Mobile, and Heineken in a similar capacity. Clearly, he was on to something. The idea that a company would pay someone to walk around the nation and stop every few feet to make sure the performance was good struck a nerve with the public. That’s a company that cares about their users’ experiences, right? (Well, at least their marketing department painted a great picture.)
Creating an Audio Test Plan
As AV professionals, we can take a page out of Verizon’s marketing department’s play book. We should keep in mind that the audio experience for our users will change depending on where they are in a space. An often-overlooked checklist item from the AV9000 Commissioning checklist is:
“There is a “test plan”, locating a representative sampling of all listener positions, with at least center and corner locations” included.
Someone reading this might think: What’s going on here? I thought this entire checklist was the “test plan”. Now you’re asking me to come up with a test plan WITHIN the test plan. What kind of Inception level, doohickey business is this?
Equal Listening Experiences
The idea behind creating the audio test plan is to recognize that not every listening position in a space is created equal. We want to keep that in mind for all the listening experience tests we do for commissioning. So, we need some type of plan to take a sampling of the listening positions in the room to assure that all listeners in a space receive an excellent experience. They will undoubtedly be slightly different, but regardless of that variance, they should still have an excellent experience.
It’s easy to visualize the different listening environments in a large auditorium space. There’s floor seating with line of sight to the central cluster. There’s the balcony which may get some contribution from the main loudspeaker cluster but might also need reinforcement from some fill loudspeakers. There’s also the mezzanine area that might need most of the audio to come from ceiling loudspeakers installed under the balcony. There might even be a lobby outside the theater that has to contend with street noise. Each section will have a wildly different audio solution that needs to be verified to assure an excellent listening experience for the users. Having an audio test plan for such a complicated space just makes sense.
But what about for a medium-sized conference room? You would be surprised at how many different acoustic areas could be found in a relatively small room. Maybe there’s an unbalanced HVAC vent in the corner of the room causing a lot of ambient noise in that corner. Maybe there’s a window on one side of the room that is letting in large amounts of street noise. Perhaps there is a curved, glass (eek!) wall in the room logarithmically focusing sound onto one or two seats at the table. What if the room only had loudspeakers by the display so the front of the room hears clearly, but participants in the back of the room are straining to hear the far end of conferences? These seemingly simple rooms can have many subspaces within them, driving the need to take a sampling of readings to confirm ANYone in the room has a great experience.
Once we have the test plan sorted, there are several audio level tests we should consider to verify the system is performing well for all users. First, we should take ambient noise measurements at each of our test locations. This is the noise that will always be present in the room that is not intended. It’s the background HVAC noise, street noise, building sounds, people talking, etc. It’s the noise we have to overcome with the audio system distributing the audio we actually want to listen to. It’s important to take ambient noise measurements at each test point so we get that room sampling to assure our sound system is loud enough for all listeners.
The next level we need to measure is the listen levels at each test point. The requirement here is that the system is producing audio loud enough for all users. To that point, each listen level measured should be at least 14 dB (ideally, 24 dB) louder than the ambient noise level at that position. We want to assure that the signal level is adequately louder than the noise level in the room so that users don’t have to strain to hear and comprehend what is being distributed. We all know how difficult it is to have a conversation in a loud bar. The signal level (my conversation) is not adequately louder than the noise level (everyone else’s conversations), so it is difficult to hear and focus on what is being said. We don’t want this for our installed systems. We want users to be able to clearly hear what is being said and have the intended audio signal level from the system be “much louder” (by at least 14 dB) than any ambient noise in the room.
Equal Listen Levels
We also want to make sure that listen levels are comparable around the room so that everyone has a similar level no matter where they are. We do not want people seated close to the displays to be blasted out of their chairs from the sound pressure in the system while at the same time, users in the back of the room are straining to hear. The tolerance of the audio coverage will vary by users and intended system use. It might be +/- 3dB for general conference spaces, or it could be +/- 1 dB in an executive space. We want every user to have a similar audio experience in the space. We need an audio test plan to verify this.
It’s not enough to pick one spot in a room to take audio measurements. Even simple rooms have counterintuitive acoustical nooks and crannies that require a sampling of locations throughout the space to assure all users have an excellent experience. That’s not to say the number of test plan locations must be exhaustive or cost-prohibitive, but they must provide an adequate sampling of the space. The nice thing about these measurements is they can be documented very quickly with an inexpensive sound pressure level meter (ideally, one that is calibrated), and they will assure all the users in the space have an easy time comprehending what is distributed by the audio system. Test Man had to walk around the country for thousands of miles to make sure we could hear him now. That is an incredible amount of work, but, as the commercial said, “It’s what makes us the most reliable wireless network in the nation.” As AV professionals, we don’t need to walk thousands of miles to make sure all our listeners are happy. We do, however, need that test plan.
LOOKING FOR MORE?
Interested in learning more about Quality Standards in AV? Continue reading The Qualiverse or get connected with us! You can contact us here or click the chat box below to connect instantly. We look forward to chatting with you!