Image

Acoustic Information

Acoustic information for Sports Halls, Community Halls, Studios, Rooms and Schools.

Sports Halls

Sports Facilities such as sports halls and gymnasiums are large open spaces built to withstand years of use for a variety of sports. They are built with hard wall, floor and ceiling surfaces making them particularly poor acoustically. These spaces are often used for a variety of activities making their acoustic performance important in order to facilitate clear communication and provide an enjoyable atmosphere whether the activity is a school assembly or one of the many sports which are carried out in these environments.

As there is an increased awareness of the importance of exercise to health, there has been a big increase in the number of people attending sports activities. This has lead to an explosion in sports building needs and has resulted in the construction of new sports facilities around the country by Councils and is encouraged by National Government policies. Health and Safety research and concerns by the Education authorities into new schools has resulted in the introduction of legislation to comply with the acoustic requirements. These are laid out in Building Bulletin BB93 and are part of the Building Regulations in the design of not just the sports halls but also classrooms, music rooms, dining halls etc.

Sports halls, gymnasiums and especially swimming pools have long reverberation times through the nature of their construction and surfaces necessary to their function. One of the prime requirements of the internal surfaces of sports facilities is that they are strong and durable. To this end, the internal wall surfaces typically comprise of painted high density block work, brickwork or timber cladding.

When sound hits these hard surfaces, it bounces back into the hall and this results in high noise levels and poor speech intelligibility. Long reverberation times also increase the reverberant noise levels within halls, which further decrease speech intelligibility. To compensate for this, people tend to increase their voice levels to in order to be heard, which further exacerbates the situation.

Poor acoustic conditions in these environments make it difficult to communicate. Fitness instructors, physical education teachers and other professionals find it difficult to cope with the high noise levels which can lead to voice problems due to prolonged use of the voice and the need to shout to keep control. It is important to have good acoustics in these areas not only for staff but also for users so they can enjoy their activities without distraction.

Schools

Recent studies have shown that many classrooms have poor acoustics. As a result, children with normal hearing are often unable to make out what is being said in class. While adults will guess at missing words, children find it much harder to fill in the gaps and their educational development can suffer.

Before 2003, Part E of the Building Regulations did not apply to schools until recently. It also requires sound absorption for entrance halls, corridors or hallways in multiple dwellings such as flats. All school buildings are now subject to detailed design checks and on-site inspections by building control officers.

Section 1 of Building Bulletin 93 describes the 'Specification of acoustic performance'. This section gives the performance targets for compliance with the Requirement from Part E of the Building Regulations 2000 (as amended):

"Each room or other space in a school building shall have the acoustic conditions and the insulation against disturbance by noise appropriate to its normal use."

Building Bulletin 93 aims to :

  • Provide a regulatory framework for Acoustics in schools the acoustic design of schools in support of the Building Regulations.
  • Give supporting advice and recommendations for planning and design of schools.
  • Provide a comprehensive guide for architects, building control officers, building services engineers, clients and others involved in the design of new school buildings.

There are three main reasons why rooms may be acoustically bad for speech:

  • They may be too reverberant for the speech sounds produced in them
  • They may be noisy because of weak resistance they offer to the penetration of noise from outside or from nearby rooms.
  • They may be shaped so that the speakers are more or less screened from their audience or part of it.

Effect of Reverberation on Speech

Part of the sound from a teacher passes directly to the ears of his/her pupils. Another part travels to the rooms surfaces and is reflected, eventually reaching the pupils ears from many directions at close intervals: this is called reverberant sound.

If there is too much reverberant sound, the pupil is still receiving the reflected sounds of previous syllables when trying to cope with the direct sound of later syllables. The two then interfere, and speech is difficult to understand. The amount of reverberation is usually expressed as the reverberation time, which is the time taken for the sound to die away after its source has stopped. It may vary from half a second in an ordinary living room to 8 seconds or more in a large assembly hall or gymnasium. Sound control in schools

A classroom or teaching space with a long reverberation time of several seconds will cause syllables to be prolonged so that they overlap and hence degrade speech intelligibility.

Long reverberation times occur in large rooms with hard wall, floors and ceiling surfaces. Adding acoustic absorption panels or tiles will reduce the reverberation time and will improve speech intelligibility. Building Bulletin 93 specifies the reverberation times required for various teaching spaces ranging from classrooms to assembly halls.

Amount of Acoustic Absorption Required

In classrooms and other rooms for speech, large amounts of fixed acoustic absorption are often required particularly where rooms have high volumes, as often occurs in older buildings. It is advisable to contact the technical department of Soundsorba Ltd so that the correct amount of sound absorption can be calculated for the space in question.

Community Halls

Technical solutions for acoustic problems in Community Centres

Soundsorba have many years of dealing with acoustic problems in Community Centres. Community Centre buildings vary quite significantly in their construction. Although a few are newly designed and built ( especially through Lottery funding ), many are older buildings which were built, possibly for another purpose but later were handed over to a community organisation to run locally needed services.

Management of Community Centres

Some Community centres are owned and run by local authorities but many of them are run by local residents who form a Management Committee. These members are mostly unpaid volunteers who really care about their community and want to give something back to enrich the lives of the local residents. As these members do not receive any salary , the time and effort they put in to run and organise activities at these community centres is invaluable.

Community centre buildings vary in their construction. Some as very basic such as a large timber shed to specifically designed and built centre which resemble sport centres. A lot of the funding to run these centre is raised by the local Management Committee.

Community Centre uses

Many of the buildings are used for a wide range of activities. These can be scout groups, local music gigs, aerobic classes, nursery use, pre-natal and health awareness sessions, jumble sales, birthday parties, small weddings and local community meetings.

The buildings need to be low maintenance, easy to clean and durable. This leads to the floors being either wooden or vinyl or similar easy to mop clean surface. The walls tend to be either bare brick / blockwork which has normally been painted or plastered or sometimes solid wood panelling. The ceiling surfaces can vary from plasterboard to concrete or metal cladding or similar.

Acoustic Problems in Community Centres

.

Whilst these surfaces are excellent for the functional requirements of easy cleaning, long term durability and low maintenance, these hard surfaces lead to a noise problem. When the hall is being used by people, the sound hits the hard surfaces and 95% to 99% bounces off back into the room. When there are a number of people in a hall, this reflected noise is amplified and makes the hall act as an echo chamber. This means that words are difficult to decipher as they are lost in the clatter of sound which is reverberating off the hard internal surfaces of the hall.

Many of the Management Committee members and users mistakenly think that there is no solution and carry on suffering from such dangerous high noise levels.

However, there are a number of solutions available from the Soundsorba range of acoustic products which will not only work but are cost effective and simple to install.

Installation of acoustic panelling

As Community Centres have very little spare money, savings can be made if the product required can be fitted by local people. Nearly all of Soundsorba acoustic products are DIY in terms of installation therefore local labour can be used to carry out the fitting work. This not only saves money but allows one to carry out the work quickly without waiting for a time window to suit a specialist fitters time schedule.

There are two surfaces where sound absorbing panels can be applied. These are the walls and the ceiling. The sound absorbing panels chosen need to be suitable for the activities being carried out in the hall.

Ceilings

(a) Echosorba II stick on acoustic ceiling panels: Providing there are no balls games to be played in the hall then the solutions will be to fit Echosorba II stick on acoustic panels on most of the ceiling area. If there are existing lights then these can stay where they are as the acoustic panels can be cut to fit around the light fittings. The same applies to fire detectors and other services. Again this is a cost saving as the lights do no have to be removed and then refitted. And we all know how long it takes to get an electrician!

The Echosorba II acoustic panels are lightweight and are simply glued to the ceiling using a contact adhesive (This is called Bondsorba ceiling contact adhesive). The application method is easy as the adhesive, which comes in a one litre can, is applied to the ceiling surface with a brush and also the back of the acoustic panel surface. This is left for about 4 to 5 minutes (depending on the temperature and humidity conditions of the hall). Once the adhesive is touch dry, then press the panel onto the ceiling surface and apply pressure evenly over the panels and especially the perimeter edges. The adhesive is instant grab therefore make sure to position the panels in the exact position. The Echosorba II acoustic panel is pre decorated in visually pleased white speckle finish and the perimeter has bevelled edges to give a special design effect. The extra advantage is that this product can be painted to a required colour by using a water based matt emulsion paint without any significant shortfall in acoustic performance.

(b) WoodsorbaPro timber acoustic panels: Where there is the likely- hood of ball games being played in the hall, then WoodsorbaPro timber acoustic panels will be a better solutions as it has better impact resistant properties then the Echosorba II stick on acoustic ceiling panels. These panels are made of wood (18mm thick M.D.F) and are supplied in board lengths of 2400mm long. The most popular width of the panels for ceilings is 293mm wide. This makes it easier to move the board over the shoulders and lighter to fix when installing over ones head. These panels are tongue on one long side and grooved on the other long side. The installation method is to screw or nail these panels through the sides and push them together to form a visually seamless joint where the fixings are not visible. There are four different face patterns, two are slatted and two are circular hole versions. The panels are available in a range of real wood veneers as well as painted finish. A paper laminate surface is also available as the cheapest range but it is only chosen on rare occasions as the paper surface is not very durable.

These panels are simply fitted to pre-fixed timber panels.

Walls

(c ) Wallsorba acoustic wall panels: These are fabric faced sound absorbing panels and are used on the vertical wall surfaces to absorb the noise in the hall. These have good impact resistance from indoor footballs etc and are available in a range of 20 new colours.

These are large panels in standard sizes of 2700 x 1200 x 25mm thick and hence are cost effective and installed very quickly as they cover large wall areas in the minimal amount of time. Three different versions are available and they differ only in their perimeter edge detail. The Wallsorba Type A Tee joint and the Wallsorba Type B Butt joint are the most popular and cost effective versions. These two versions are also the most flexible as they can be cut to size on site with a Stanley knife to suit the height and width of the walls.

These panels are also fitted in community centres where the panels are fitted on their sides ( i.e horizontally ) in a 1200mm high band around the four walls, wherever possible.

(d)Echosorba II stick on acoustic ceiling panels: These can also be used on walls at high level where they are out of reach and not likely to be hit by any objects. These are fitted horizontally or vertically to suit the free wall area which can be covered. Details as on the ceiling above.

(e) WoodsorbaPro timber acoustic panels: These can be fitted at low level as they are very durable and are the most resistant acoustic panelling product in the whole range as they are made from 18mm thick timber. Details as on the ceiling above.

How much sound absorption is required ?

Community centres do not tend be large halls nor are they small rooms. The acoustic environment can be tuned to suit a particular usage for the hall. Lets take the example of a typical community centre hall. This hall has internal dimensions of 20 metres long x 10 metres wide and 4 metres high. The floor is timber boarding , the walls are plastered and the ceiling is made from plasterboard. The existing reverberation time in this hall is around 2.9 seconds at the important 500 Hertz mid frequency. If the hall is going to be used for music (live singing and musical instruments ) then the reverberation time needs to be reduced to about 1.4 seconds. However , if the hall is going to be used for speech (such as debates and functions ), then the reverberation time need to be reduced even lower to 0.8 seconds.

So if the community centre hall is going to be used as a multi-function hall then which reverberation time should you be trying to achieve.

The answer is the you have to have a compromise reverberation time of around 1.1 seconds which is almost good enough for speech but also live enough for music.

To achieve a reverberation time at the mid frequencies of around 1.1 seconds, you will need to install 90 square metres of Echosorba II stick on acoustic panels. These can be on the ceilings or on the walls or parts on the wall and part on the ceiling. The important point is that you introduce a minimum of 90 square metres into the hall and that this absorption is evenly placed around the hall ( i.e. all the acoustic panelling must not be installed in only one end of the hall ).

But my Community Hall is different ?

Soundsorba can help calculate the exact amount of absorption if you can email the exact internal dimensions of the hall along with the description of the surface finishes of the walls, floor and ceilings. Digital camera photographs emailed will also be extremely useful. This is a free technical service which we provide to help of customers avoid costly mistakes so that they introduce the right amount of absorption into the hall.

Which Community Centres have used Soundsorba acoustic panels ?

Just a few a listed below :

  • Great Chesterford Village Hall
  • Vivian Moon Community Centre
  • Tring Park Cricket Centre
  • Hoar Cross Hall
  • Flitwick Community Hall
  • Taunton Amateur Opera Society Hall
  • Fulde Coast YMCA
  • Royal Burnham Yacht Club
  • Ember Brook Community Centre
  • Whiteleaf Scout Group
  • Horton Cum Stanley Village Hall
  • Bellyman Art and Community Centre
  • Islanders Boys Centre
  • 3rd Hampton Scout Hall
  • Berkshire Young Musicians Centre
  • St Issey Village Hall
  • Marsworth Village Hall
  • Ist Newent Scout Group Hall
  • Shelley Farm Community Hall
  • Thorpe Marriott Neighbourhood Centre
  • Castlefield Challenge Community Centre

Studio Acoustics

All studios need to be protected from sound transmitting into and out of the studio from surrounding areas but additionally it is important to consider the internal acoustics in order to promote sound quality. It is also very important to differentiate between the two problems as a product for sound absorption will not be an effective product for sound insulation and vica versa. Failure to correctly diagnose the problem can lead to expensive retrofits.

Some of the common acoustic problems within studios include long reverberation times, early reflections and standing waves.

If the reverberation time in a room is too long then there can often be distortion and harshness in the recording however if the reverberation time is too short, the recording will sound very flat and dry. The correct reverberation time for a studio is typically 1/2 to 1 second depending on its size.

Early reflections within a room occur when a reflected sound arrives at a slightly different time to the direct sound making the direct sound unintelligible.

Standing waves occur in areas where there are parallel surfaces and the sound repeatedly bounces between the same two walls when two sound waves of the same frequencies interfere with each other they become stationary causing an imbalance in frequencies, strengthening some frequencies but cancelling out others.

The most effective method of reducing these effects is through absorbing and diffusing the sound waves in order to prevent them bouncing between surfaces and creating long reverberation times, standing waves, early reflections and also 'dead spots' or areas within the studio where swound is weak or cannot be heard clearly.

Absorption

Absorption products help to eliminate sound waves from reflecting off hard surfaces by absorbing them. In studio environments there are many different frequencies which need to be absorbed this is why Soundsorba developed the Studiosorba range which consists of high performance acoustic foam products for the absorption of medium, high and low frequencies. The range of sound absorbers offers great absorption combined with superb designs which bring character to the room.

Diffusion

It is important to keep the studio sounding live. Too much absorption can create a space which is dead and as well as being comfortable to work in it will aslo produce very flat recordings. Combining absorption with diffusion is an effective way of achieving the right balance.

Diffusers reflect or diffuse sound across the space evenly contributing to the reduction of reverberation and standing waves without taking the energy out of the room. The new Diffusorba range has been specifically designed for this purpose. There are two designs within the range which can be mixed and matched together and with the Studiosorba range to create visual effects and exceptional acoustic control.

Room Acoustics

The sound within a room is a combination of direct sound which is emitted from the source and indirect sound, reflecting off hard surfaces within the room. Once emitted from the source, sound waves travel through the air until they reach a boundary surface or other obstacle. When the sound wave hits the surface it will be partly reflected off the wall and back into the room in a new direction and it will be partly absorbed by the surface with the absorbed energy being dissapted as heat.

In some cases reflected sounds can be desirable as they can be used effectively to strengthen the direct sound however reflections can also distort sound and create comfortable and ineffective listenings or recording environemnets. Too much reflective sound can cause echo and reverberation within the room. Echo can be described as a delayed repetition of a sound however when these repitions build up and become inaudible, this is called reverberation.

The reverberation time in a room is the time it takes for the sound to decay by 60dB. If the reverberation time is too long then it makes speech very difficult to understand and the more difficult it is to communicate or record effectively. If the reverberation time is too short then the room can sound lifeless.

The most reverberation areas are those constructed with hard surfaces because the surfaces do not absorb much of the sound which hits them. In large areas with acoustically hard parallel surfaces, flutter echoes can occur, significantly increasing the reverberation time and reducing speech intelligibility.

The amount of sound energy which is absorbed by a surface is given by its absorption coefficient. A surface which absorbs no sound at all will have an absorptiobn coefficient of 0; this would be a totally reflective surafce. A surface which absorbs all of the sound energy which hits it has an absorption coefficient of 1. These are often expressed in percentages and the higher the value the more sound will be absorbed. A plastered masonry wall has an absorption coefficient of about 0.02 or 2%, which means that it absorbs 2% of the incident sound and the rest is reflected back into the room.

The most common method of dealing with problems like echo and reverberation is to absorb them. Applying porous materials to the walls and ceilings will reduce the reverberation levels by absorbing most of the incident sound, therefore reducing the level of sound which is reflected back into the hall.