Circuit Park Zandvoort (CPZ) operates under a licence issued by the Province of North Holland as part of the Environmental Protection Act. As might be expected, this licence focuses on the noise originating from the circuit. The noise produced by the circuit has been drastically reduced in recent years by introducing a noise control programme that has involved putting enormous noise-protection dams and screens along the track, as well as making the use of exhaust silencers compulsory where possible. The rules that the CPZ has to comply with are relatively simple and can be explained as follows (a calculator will later make things clearer):
 
- 360 days per year the CPZ may produce a maximum LEQ* of 55 dB(A) per day (from 07.00 hours to 19.00 hours) on the outer wall of the nearest permanent construction (Burgemeester van Alphenstraat). This standard therefore applies both during the week and at weekends, irrespective of the type of activity on the track.

- 5 days per year the CPZ may produce an LEQ higher than 55 dB(A) per day on the outer wall of the nearest permanent construction. These days are currently used for the two large(r) international events, like the Marlboro Masters of Formula 3 and the D.T.M.
 
* Equivalent sound pressure level LEQ = a theoretical constant sound level that produces as much sound energy within a certain period as that which is actually emitted. For more information about calculating noise click here.

An LEQ value is actually nothing more than the measurement of a weighted average over a specified time period.

Throughout the entire year, CPZ is subject to an evening standard (19.00 to 23.00 hours) of 50 dB(A) and a night-time standard (23.00 to 07.00 hours) of 45 dB(A).
By complying with a set LEQ value, the CPZ can arrange the daily programme as it likes, by for instance giving relatively quiet cars a lot of track time or by giving noisy vehicles very little time.
Two examples that meet an LEQ of 55 dB(A) are as follows:

- 10 cars each emitting 80 dB(A) can collectively do 55,000 laps per day on the CPZ.

- 10 cars each emitting 100 dB(A) can collectively do only 550 laps per day on the CPZ.

The most important difference between the two above examples is that the first is scarcely audible outside the CPZ but the second is. Both examples do however comply with the terms of the CPZ’s licence. In absolute terms, there is no difference in the noise produced per day. In relative terms, the first example is experienced as less of a nuisance than the second.

Noise produced by the CPZ is measured at a point located immediately next to the track (where cars turn onto the straight). Taking measurements here ensures the wind’s influence on sound levels is kept to an absolute minimum. An independent research agency and the Province of North Holland have established that the difference between the noise measured along the straight end and the outer wall of the nearest construction is 26 dB(A). By determining this interim value, Circuit Park Zandvoort can measure noise close to the source itself (cars and motorbikes), without having to worry about ambient noise.
Noise generated at the CPZ is mostly measured on weekdays and electronically converted into an LEQ value in the evening. Based on experience, the CPZ can nonetheless determine what can/may drive on a particular day without having to measure noise levels.

For official events, the CPZ is obliged to calculate the expected noise level beforehand and submit this to the Province, which must confirm that the prospective programme meets the terms of the licence. Noise is constantly measured during events and the results have to be submitted to the Province later.

Standard noise levels for both the evening (19.00 - 23.00 hours) and the night (23.00 - 07.00 hours) are of course substantially lower than during the day, i.e. 50 and 45 dB(A) LEQ respectively. The licence expressly forbids activities on the racing circuit during the night (24-hour races are therefore not permitted). By establishing an evening and night standard, use of the CPZ is more limited than during the day.

In the calculator on this site, the permitted maximum daily standard of LEQ 55 dB(A) represents full capacity use. It should be borne in mind that every pass of the measuring point/ microphone contributes to the total noise measured. If the number of cars driving is therefore entered into the calculator along with the distance of the race (i.e. the number of laps) and the amount of noise produced per vehicle, an insight is gained into what the specific race ‘consumes’ from the available daily total. By doing this, a programme for the day can be drawn up by ‘playing’ with the different variables.

As an example, you can download a calculator that has already been filled in. You can alter this to see the effect of changing the different variables.