Acoustic Measurement Tool for Public Health

Springwell Audio Services has recently acquired a new tool to help event organisers, music venues and PA companies stay within noise exposure limits set by local authorities. RTCapture is a PC based software solution from the Wavecapture team which can accurately monitor and record sound pressure level (SPL).

Night clubs, restaurants, live music venues and live concerts can all potentially generate a high sound levels for visitors. It is required that the person responsible for the facility takes appropriate measures to protect the hearing of patrons. One aspect is to control the audio generated by sound systems. Generally, but not always, the sound from a public address system is louder than the audience or public and it is reasonable to assume that controlling these levels will provide the largest benefit.

However, it is not the whole solution. Room acoustics is a key aspect that is often overlooked. An enclosed space that has a long reverberation time will sustain the noise level experienced by patrons, as it takes longer for the acoustic energy in the room to decay. Adding absoprtive materials can reduce the noise levels and create a more intimate atmosphere. This is a simplistic example – the services of an experienced acoustic consultant should always be sought before making changes to a room.

Beyond room acoustics, there are several methods of controlling SPL in a venue. The first takes the form of electronic hardware that can limit the SPL produced by the sound system in the venue or performance area. These automatic ‘levelling’ devices monitor and control the amplitude of electronic audio signals and the acoustic SPL, reducing excessive levels to an acceptable acoustic output. Another method is to monitor levels as previously but switch off power to the amplifiers when levels exceed a certain threshold for a given length of time. This is usually preceeded by a warning indication (a yellow light, for example) but if the warning is ignored, the results are catastrophic for the performing artist on stage or people on the dance floor.

The latter method often results in the system being bypassed or disabled in one way or another. The hearing protection the system once offered is now removed and patrons will possibly experience noise doses that can cause permanent damage.

One example of a measurement setup. Laptop with RT Capture Software, Digigram VX PocketV2 Audio Interface, Measurement Microphone. Using a self powered microphone such as the MiniSPL from NTI Audio negates the need for phantom power

One example of a measurement setup. Laptop with RT Capture Software, Digigram VX PocketV2 Audio Interface, Measurement Microphone. Using a self powered microphone such as the MiniSPL from NTI Audio negates the need for phantom power

Another option that can be employed alone or as a complement to automatic controls, is self monitoring. This simply means that the SPL at a venue or event is recorded and can be checked throughout an event. Previously, an expensive sound level meter was required to perform these measurements. Now, a more cost effective PC based solution is available. All that is needed is the appropriate software, an audio interface, omnidirectional measurement microphone and a low noise microphone preamp. The system must also be calibrated to ensure the correct levels are recorded and that the system meets the requirements of the authorities.

RTCapture is a software package that provides a Real Time Analyser (RTA) function  and an integrating Sound Pressure Level (SPL) monitor. It is primarily aimed at the live music market, being used at the Front of House mix position. However, it is also very useful and recommended for logging of SPL at night clubs, restaurants, pubs and other venues where music is played at high levels. Users can see how ‘loud’ it is in their venue and take measures to adjust the sound system accordingly.

A unique and novel feature of the software is a ‘Remaining Leq’ calculation. This provides an accurate indication of whether or not the user will exceed the ‘Leq budget’ for a predetermined time period. This is extremely useful for front of house engineers who can keep a careful watch over the event levels and ensure conformance with local regulations. It’s also a good way to put off those concert goers who always ask the engineer to turn it up!

Springwell Audio Services can provide a complete measurement solution for a live music event, including an engineer who will calibrate the system and offer advice on noise management. We will also make measurements to enable any necessary corrections to be made for the end of event report.

If you wish to purchase a system for use in a permanent location, we can recommend suitable hardware as well as provide a full installation and calibration service. Our  calibration equipment has a fully traceable history.