Scott Sugden (SS): From a design standpoint, the key strategies to control sonic spread are increasing source directivity and/or decreasing the energy projected per source via a distributed approach. In all cases, it is very important to obtain the information necessary to produce well-defined system specifications.
How much SPL is needed per audience area and what are the level limits in the far field? What is the programming and what are the projected size, density, and aesthetic expectations of the audience? What are the artists’ expectations? The answers impact the design options available and allow us to anticipate potential issues that may arise and plan for maximally effective and minimally intrusive ways to address them.
Aaron Davis (AD): Beyond system design, we also work closely with the festival design team on the layout and composition of site elements to direct, reflect, scatter, and/or absorb sound energy in ways that reduce sonic bleed into undesirable areas. Finally, anticipating how noise may escape our control, alerting the community to the possibility, and devising possible response plans help us raise the twin pillars of expectation management and preparation, which are essential when things go wrong.
Pantelis Vassilakis (PV): Striking a balance between meeting artist/audience aesthetic expectations and complying with noise ordinances may be the holy grail of open-air music festival sound system design. The ideal would be a system resulting in a spectrally uniform spread of sound away from the stage, with minimal level changes within a pre-defined audience area and maximum level drop with distance outside that area.
Loudspeaker system design and deployment strategies that are informed by interference theory, hearing physiology, and the psychoacoustics of loudness perception represent efforts of a varying degree of complexity and sophistication towards these objectives. During KAABOO, it is very rewarding to work with a team that has the implementation and verification know-how to take theory to practice. Beyond science and technology, it is all about managing expectations and getting comfortable with the reality that community noise and annoyance levels do not necessarily correlate, especially in the case of music versus, say, traffic noise signals.
PSW: How about imposing SPL limits at FOH? What are the talent expectations and how can such limits be communicated and implemented in a positive way?
PL: I think FOH SPL limits are becoming increasingly common and therefore experienced sound engineers are familiar and at peace with them. In general, Solotech focuses on monitoring of any necessary limits and implementing relevant design components that minimize the impact on the artists and audience. It is never fun to learn at the last minute that the Ferrari we got you is “locked” at 60 mph! So, early communication, buy-in, and formal agreement on such limits are very important, indeed.
AD: Absolutely, in our experience, SPL limit language must be agreed upon during the contract negotiation process to be effectively enforced on site. Limits and procedures are clearly communicated, in writing, to the artist production management teams prior to the event, followed by on-site conversations with artist staff upon load-in.
Clearly visible signs and SPL meters with easy-to-read limit displays allow artist engineers to comply without having to focus away from the mix. The goal is to eliminate any ambiguity, allowing the artist engineers to prepare (inserting mastering compressors, spreading the energy across multiple EQ bands, etc.) so that SPL limit compliance does not interfere with the audience experience.
PV: Reducing the overall level at the source is the single most important measure towards improving community noise threshold compliance. Thankfully, FOH levels registered during most large outdoor festivals are sufficiently large (≥105dBA & ≥117dBC 5min Leq at ~120ft) to permit a reduction that can produce perceptually and numerically significant attenuation at large distances, but barely noticeable loudness changes for the audience: our hearing’s intensity discrimination threshold is much finer at the levels reaching the surrounding communities than at FOH.
A positive side-effect of such reduction (≤97dBA & ≤110dBC 5min Leq at ~120ft) is that audiences will perceive the music as loud and clear for longer—the hearing protection mechanism will kick in after longer exposure than it would at higher source levels—resulting in a win-win for talent, audiences, and the community! Convincingly communicating this to talent, getting their buy-in, and reliably enforcing agreed upon limits has gone a long way towards gaining the support of the communities surrounding KAABOO.
