Noise emission management.

Visit any pro audio loudspeaker manufacturer and thick plywood disks of varying sizes will undoubtedly fill the recycling bin. What to do with these unwanted driver cut-outs is a perennial dilemma. In similar fashion, there are always chunks of sound that are entirely unwanted; ask anyone who lives within five kilometres of a regular festival site. These days, most of the 'noise' loudspeakers make is highly focussed on delivering the best listening experience possible to the target audience. But what of the excess sound? The means to measure and monitor is well established, but predicting and correcting before it occurs is surely a more favourable outcome.

Prediction for consultants

The current tools available for examining sound propagation over distance have evolved from industrial applications with many ill-suited to assessing the output of a typical modern line array system with its attendant subs, fills and delays.

Prediction for system technicians

From all leading pro audio loudspeaker manufacturers and some independent sources there exists an abundance of tools that calculate SPL distribution for the audience area based on analyzing system design (as applied to the venue), EQ, directivity characteristics, and delays. However, none of these address the wider field, outside the audience area, or can account for the effects of weather and topology.

A combination thesis

The situation raises a number of dilemmas, not least the tension between artistic freedom (paying concert goers do not want to listen to Rammstein at a miserable 85dB(A)), and socio-cultural sensitivities (that undefined segment of the population who would prefer never to hear Rammstein at all).

They also point to a solution: remove the disconnect between the system technician and the noise consultant. To coin a phrase, what both parties want is more art, less noise.

Solution

The technical foundation underpinning NoizCalc derives directly from ArrayCalc. This familiar d&b tool provides a sophisticated view of the performance and propagation of d&b loudspeaker systems. As part of its calculation ArrayCalc considers typical factors of loudspeaker layout, directivity, delays and EQ, plus phase data. If one's calculation includes the issue of phase then the underlying prediction is complex by definition, but the outcome is a far more accurate reflection of what can be expected anywhere, from any frequency, at any time within the listening area. If phase is not considered, as in industrial noise calculations, the data is over simplified and somewhat redundant as a means to predict noise from sound reinforcement systems.

Using this complex data from ArrayCalc, NoizCalc software models noise pollution outside the defined listening area using two widely adopted noise propagation standards. ISO 9613-2 assumes a worst case scenario; imagine winds blowing in all directions from the source all the times. Nord 2000a meanwhile, is a more sophisticated standard which takes real world meteorological conditions, such as the current wind direction, into account for a more applicable prediction.

Talking to the authorities

d&b NoizCalc was developed in direct collaboration with SoundPLAN GmbH, a specialist software team concerned with environmental noise pollution and prediction. SoundPLAN sofware can, like NoizCalc, import data from ArrayCalc simulations and accurately calculate what will be heard from d&b systems, including at distant locations.

Whereas NoizCalc produces a momentary result based on the given sound system setup and the prevailing conditions at that time, SoundPLANnoise is looking at day’s time histogram. It is the measurements over time that have meaning for the authorities. We leave SoundPLANnoise to look at what is happening across a defined performance. It is important that in acting on behalf of the concerned authority they retain their independence and provide objective data. 

Glide like a swan while NoizCalc paddles furiously beneath the surface

If using NoizCalc it is important to know what data to import alongside the ArrayCalc project data. For example Google Earth helps get a feel for the lay of the land and its contours, as well as how to draw buildings and define the nature of the environment, whether shaped by asphalt, grass or trees. But don’t get too hung up on detailing each tree in its exact location; slopes and buildings and temperature gradients have greater influence. More useful still is wind speed and humidity. Furthermore, saving such data over time will build a resource for assessing changing meteorological conditions and system noise when working onsite.

It is also possible to define the spectrum of music in NoizCalc, such as heavy rock, acoustic or folk, and input an assessed FoH level at the desk to guide how the system will be working everywhere else. So yes, there is work to do, but by inserting NoizCalc directly into the d&b Workflow, next to ArrayCalc and between R1 and the amplifiers, all the heavy lifting goes on in the software. It is a new way of thinking about sound beyond the audience environment. Just don’t be surprised if the issue of noise control becomes a fixation, with traffic noise and other previously sublimated sounds suddenly becoming conscious preoccupations.

Main benefits:

  • gain a better understanding of what causes problems with noise and perhaps prevent them
  • demonstrates to the authorities an awareness of noise concerns, making approval processes easier
  • enables clearer communication between technicians, consultants and local residents 

Download d&b NoizCalc