With over 100,000 revellers and round-the-clock music and partying, Glastonbury Festival is an environmental health challenge on an unprecedented scale. Curtis Lakin, Stuart Brown, and Martin Williams look at the specific problem of noise control

In 1970, for an entrance fee of just £1, around 1,500 "free spirits" enjoyed a weekend of live music. Almost three decades later, and at greater expense, over 100,000 people can now enjoy the atmosphere of Europe's premier outdoor music event. With more than 250 acts performing on 10 stages, alongside a range of other attractions from cabaret, theatre, comedy and circus to children's activities, this is Glastonbury Festival millennium style.

Glastonbury Festival is mainly recognised for its formidable line-up of contemporary chart-topping bands. There are, nevertheless, many more attractions contained within this 700-acre green field site, which is bounded by over five miles of double layer security fencing, complete with watch towers. The festival is also home to some 800 traders for the weekend, and provides over 1,900 portable toilets and approximately 10 miles of pipework to supply mains water across the site.

Since 1970, Mendip District Council has had the unenviable "privilege" of both licensing and monitoring this massive public entertainment event. This process alone, which involves the drafting and monitoring of almost 200 conditions, requires not only careful planning over a period of six months or more, but also the use of over 80 staff, many of whom are recruited from outside the Mendip Council area.

Noise is only one of many aspects that the council must seek to control by way of conditions (there are currently 15 specific conditions attached). However, it is undoubtedly one of the few areas which, if it goes wrong, has the potential for causing the greatest disturbance to nearby village residents. The question for the council, therefore, is how do you effectively control noise from ten open air stages, countless additional attractions and some 800 market traders, many of whom have their own sound systems with combined sound power outputs of in excess of 30KW? Not to mention the additional general noise associated with over 100,000 permitted festival-goers.

Many years ago, before the Noise Council's Code of Practice on Outdoor Music Events was even in its embryonic stages, the festival was limited to an off-site noise condition of 60dBLAeq (15min) measured at a nearby residential property. This condition was specifically designed to control noise from the "Pyramid Stage", which was destroyed in a fire shortly before the 1994 festival. The "Main Stage" which replaced it was used for five subsequent festival events, then for the millennium a new Pyramid Stage was constructed. The logic behind the 60dBA limit has unfortunately been lost in the midst of time. However, the level has been found, over a long succession of events, to correlate very well with a basic "no nuisance" criterion and therefore continues to be the yardstick on which the off-site noise conditions continue to be based.

As the event has grown, and with it the number of stages (from one to ten), there has been a need to expand the number of locations at which the 60dBA limit is applied in order to control noise from all sources. While this has been achieved with little difficulty in practice, the reality of subsequently monitoring such a limit is somewhat more challenging. The line-up of bands on each stage is such that music is almost continual between 10am and 12.30am daily (with a midnight finish on the Sunday). Monitoring now takes place at four off-site locations over a period of three days.

The process of control involves the on-site and off-site deployment of teams of officers, equipped with radios which can often be temperamental, with the specific task of ensuring that off-site noise levels are not exceeded. This requires the on-site teams to establish a level (LAeq(1min)) at the mixer positions (or "front of house") which correlates with non-exceedance of the off-site limit. Continual dialogue between the on-site and off-site teams over the duration of the event thereafter, should ensure satisfactory compliance.

However, this task becomes considerably more onerous when one considers that not only must the on-site teams negotiate the huge crowds moving around the site; but also, the off-site team, equipped with a suitable four wheel drive vehicle, must similarly negotiate off-site congestion and confusing one-way systems. The combination means that circumnavigating the site alone can typically take over an hour. In the context of this, it is perhaps not surprising that the monitoring of noise during the millennium event involved some 25 officers employed over 70 shifts.

For many years, the off-site noise monitoring locations have been equipped with "continuous noise analysers" programmed to monitor a range of statistical parameters averaged over 15 minute periods. While this has been generally acceptable, there are clear disadvantages to this method of monitoring:

• they require regular officer attendance in order to adequately monitor the event;
• they are not real-time measurements; and
• they do not benefit from the capability to carry out real-time frequency analyses.

For the 1999 festival, in an attempt to overcome these problems and to generally improve the efficiency and effectiveness of noise control, the council conducted a trial of a remote noise monitoring system which was under development at the time.
The system consisted of an outdoor microphone which could feed acoustic and calibration signals to a "Type 2260B Investigator", which was linked to a GSM mobile telephone. A laptop computer, running "Type 7820 Evaluator software", completed the system and was located at the temporary environmental health office positioned within the festival site itself.

The real-time noise analyser (a "Type 2260B Investigator") was set to measure and store a vast range of noise parameters, including one third octave frequency analyses, at five-minute intervals during the sound tests, and at 15-minute intervals at all other times. In this way, the current and past results were available at any time by requesting the Evaluator software to call the monitoring station and download its latest measurements. This procedure resulted in many practical benefits to the environmental health teams, including:

• instant access to results, without the need for difficult and time-consuming journeys to remote monitoring locations;
• the ability to give an immediate response to the sound engineer's requests to increase the volume. Indeed, where necessary, changes could be monitored immediately at the appropriate location and quick decisions made;
• identification of extraneous noise within the ambient noise profile by referring to simultaneous frequency analyses; and
• the ability to interrogate the stored information during the post-event period, and during quiet periods of the festival.

The noise monitoring system on trial by Mendip was a completely independent system which required no challenging connections, other than the site office land line telephones. However, a strong GSM network signal is required and this is very much area dependent. Without doubt, the system proved to be highly successful in permitting considerably more effective and efficient control of noise from the main stage. It permitted not only a quick assessment of complaints, but also facilitated a quick response to the sound engineers' inevitable requests for increased amplification.

Looking ahead, the potential for such a system is considerable, at Glastonbury Festival and also for other applications. In particular, the following are highlighted as potential developments and uses:

• general-purpose short to medium-term automatic monitoring of any noise-sensitive event (eg music festivals, pubs and clubs, motor sports, and water sports). It is likely that it will soon be used by the council to monitor a new Noise Abatement Zone;
• monitoring and control of low-frequency noise for music festivals - immediate effects can be observed from the remote station and mixers adjusted accordingly;
• recording of the audio signal at the remote station for subsequent replay or analysis; and
• noise source location investigations by observing the (remote) effects of switching on and off potential sources in turn, or comparing frequency spectra.

The introduction of relatively low-cost remote noise monitoring, using general purpose noise measuring instrumentation, has opened up a whole new way of controlling environmental noise. These same techniques have already been used to help minimise the effects of noise on Mendip District Council's residents in 1999, and again in 2000. In the future, it is highly likely that remote noise monitoring of this kind will become a permanent part of all festival events.

For further information regarding noise control strategy for Glastonbury Festival contact: Curtis Lakin, Mendip District Council, Cannards Grave Road, Shepton Mallet, Somerset, BA4 5BT. Tel: 01749 334912, Fax: 01749 334919, E-mail: lakinc@mendip.gov.uk

The equipment discussed in this article was supplied by Brüel and Kjaer, a world leading manufacturer and supplier of sound and vibration products for use in a wide range of applications. These include: environmental noise measurements, building acoustics, vibration measurements and quality control for use in the automotive, aerospace and consumer industries as well as by local authorities. More information on sound monitoring equipment can be obtained from Barbara Dancer, Brüel & Kjaer, Bedford House, Rutherford Close, Stevenage, Hertfordshire SG1 2ND. Tel: 01438 739000, Fax: 01438 739099 or E-mail: info@bkgb.co.uk Web site: www.bksv.com