Now hear this: How to verify audio system performance14 August 2015
A guide by verifying audio system performance, written by InfoComm volunteers and industry experts for PSNTraining
You developed an audio system for a client that took many hours to perfect. You step back, gaze upon your masterpiece and nod in satisfaction. You’re done, right? Not so fast.
Before you can turn that system over to the client, you need to verify that its performance meets requirements – and doing so involves more than just the system itself. Not only do you need to test the system, but you should also verify that the project is in compliance with industry norms. How do you do that in an organised and sequential manner?
Needless to say, no two audio systems are the same. There are many different aspects that might require verification, depending on the installation. Here are just five items that might need your attention:
- Emergency systems muting
Making sure that a muting system works properly is key, should the need to use it arise. Proper testing of such a system typically occurs at three stages of the project: the pre-integration phase, the systems integration phase and the post-integration phase. Verifying a system in the second and third phases usually entails some kind of simulation and checking to see if the audio system can mute on command.
- Audio buzz and rattles
Buzzing, rattling and other annoying noises can impact the quality of an audio experience. To check for audible rattling, you would need to simulate the conditions that may trigger it and operating the system at 3dB below the onset of distortion. The same can be done to test for buzzing, but without playback. You’ll find the system either passes or fails your test.
Reverberation time, or the time in which the sound pressure level of a given frequency decays, is an important measure of audio performance in a space. It’s vital that you properly evaluate the reverb in a room because correcting the issue down that road can be costly. Different factors effect reverberation, such as room materials and aesthetics. Testing reverberation usually requires an impulse noise to determine the reverb time within a room with a time meter. Depending on the location, it should comply with one or more standard.
- Acoustical ambient noise
Whether you’re in a conference room or a large venue, ambient noise is a big factor in the AV experience. Too much ambient noise can greatly affect the effectiveness of your audio system. Ambient noise can include sounds from neighboring rooms, HVAC systems or outside noise. In smaller areas, AV equipment itself can be a source of ambient noise. To ensure accurate analysis, tests should be performed under normal conditions. HVAC systems should be operating normally, with windows and doors opened and closed to replicate different scenarios. With the sound system switched off, analyze the noise using an SPL meter/spectrum analyser. Report the results and compare them with the recommended noise criterion.
- Microphone physical alignment and placement
When setting up microphones, be mindful of their placement. Unlike the items above, a formal test isn’t required here, but it is something to think about. To determine if your microphone placement is ideal, ask the following questions:
- Are the microphones in the locations specified in the system documentation?
- Are the microphones close enough to where people will speak?
- Are the microphones aimed in the proper direction?
- Is the proper microphone type used in the right location (eg cardioid, omnidirectional)?
- Are the microphones directed away from loudspeakers – and at a proper distance – to avoid feedback?
- Are ceiling microphones installed in low-noise environments where they can pick up the local talker louder than the background noise?
And that’s just five things to verify before an audio system is really ‘complete’.
The InfoComm International standard, ANSI/INFOCOMM 10:2013, Audiovisual Systems Performance Verification, includes 31 verification items pertaining to audio systems, including areas such as capturing, transforming, or reproducing program audio; audio signal management; acoustic environments; and loudspeaker operations.
Of course, the audio system is often just one piece of a complete AV installation. The standard includes 160 total verification items. To help you navigate and implement them, InfoComm volunteers have published the Audiovisual Systems Performance Verification Guide, which includes even more guidance on the five audio items discussed here. The guide ensures functionality and performance in accordance with a system’s project documentation by outlining the verification reporting process from start to finish. Download it today from www.infocomm.org/cps/rde/xchg/infocomm/hs.xsl/40440.htm and make sure your AV systems – including audio systems – are operating at peak performance.