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Soundfield and voice reinforcement

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Soundfield solutions

Audio visual manufacturers have brought out solutions to help teachers amplify their natural speaking voice.

In the picture above left, you can see a classroom with interactive whiteboard at the front of the class and speakers in the corners of the room.   Alternatively, you could have wall speakers mounted down the side of an interactive whiteboard, or use an integral whiteboard with short throw projector and sound.  

PA systems, such as those shown in the pictures second from the left and second from the right, provide a hand-held (or lapel, collar or headworn) wireless mic and powered speakers.  Depending on the size of the room, additional wall speakers may be needed so that people at the back of the class can clearly hear what is being said, without deafening people at the front.

One manufacturer has produced an Armstrong ceiling tile which incorporates a speaker or speaker and amplifier in the back, as shown in the picture above, third from the left.  With a choice of radio mics, you can buy a package for different size rooms.  These are fine provided you have a suspended ceiling using Armstrong tiles.   Alternatively, you could use ceiling speakers, as shown in the picture above right and second from the right.  You then choose a microphone.  Audio main comparison chart page


Soundfield and the USA

In the USA , schools and colleges have long had PA systems; perhaps you remember seeing one being used in the film ‘Grease’.  

A survey was undertaken in the USA which proved that pupils grades increased by up to 45% when the teacher’s voice could be heard clearly, especially by pupils who sat towards the back of the classroom and also those who had some form of hearing difficulty.  Even having a bad cold can cause some temporary hearing loss. Also, teacher’s benefited from being able to use their normal voice, which was amplified within the classroom or school hall, without having to raise their voice or shout.

I can only assume here, that the term ‘sound field’ was derived to mean a field of sound around a classroom and to distinguish it from PA systems which were already in use.  When the school receptionist wanted to remind pupils throughout the school about an after-school activity or to inform parents to make their way to the school hall for the PTA meeting, then the PA system would be used, and this would be different from the speakers, amplifier and microphone used in each classroom by individual teachers.

Health & Safety legislation in the UK

However the term ‘sound field’ came about, legislation was introduced in the UK as a result of Health & Safety concerns over teachers’ voice fatigue and children under performing, as a result of not hearing teachers clearly, especially those pupils sitting at the back of the class.

It is now Law that some sort of sound field / voice reinforcement system must be provided in all new school buildings, and I quote:

‘Government Specification of Acoustic Performance in Schools: Section 1 of Building Bulletin 93, the Governments Specification of Acoustic Performance sets the standards for the acoustics of new buildings and explains the requirements and solutions to... provide acoustic conditions in schools that facilitate clear communications of speech between teachers and students. The key aim of a (speech reinforcement) system is to increase the loudness of the direct sound, particularly for more distant listeners, whilst keeping sound as natural as possible. The distribution of loudspeakers and their directional characteristics is a key issue in achieving high speech intelligibility. For large teaching rooms and lecture theatres, loudspeakers can be distributed in the ceiling...’

To recap, all new school buildings MUST have some form of system for amplification of the natural voice.  Legislation for retrofit systems is likely to follow.   So what actually constitutes a speech reinforcement system?   This seems to me to be a rather ambiguous area.

According to the extract above: ‘key aim of a speech reinforcement system is to increase the loudness of the direct sound’, seems to indicate the teacher would need some form of microphone to speak into, an amplifier and loudspeaker.  It also says that for large teaching rooms and lecture theatres, loudspeakers can be distributed in the ceiling.

A teacher could wear a wireless lapel microphone and a belt pack receiver which would enable him/her to walk round the room, speaking naturally, without the risk of anyone tripping over wires. 

When it comes to the amplifier and loudspeakers, it depends on whether you want an installed ceiling or wall system or a portable PA (public address) system.

Installing loudspeakers and an amplifier in ceiling tiles in a false ceiling may help deter theft, whilst a portable PA system means you have flexibility to use it in a classroom, school hall, or for weather resistant models, poolside or school sports day.

Something to consider when using portable PA systems is where the unit is placed in the room.  When the volume is turned up so that pupils at the back of the room can hear, it may be too loud for the pupils at the front of the room.  Some portable PA systems have optional extension loudspeakers so that the main unit can be positioned at the front of the room with another loudspeaker further down the room so that all pupils can hear clearly when the volume is at a level that enhances the natural speaking voice. 

Any schools contemplating retrofit systems, i.e. changing a multimedia projector but using the existing ceiling mount; replacing ceiling speakers, wall speakers or simply buying audio equipment, needs to know that whatever they spend their money on will be future proof, in that it will comply with any legislation regarding speech reinforcement.  Interesting is that ‘sound field equipment for classrooms’, is already appearing on tenders for equipment.

Soundfield / PA solutions

Here is what we have discovered, at the time of writing:

i-ceilings sound panels

Wireless microphones

Ceiling loudspeaker

Portable PA systems with wireless microphone

SmartBoard with short throw projector and audio

Interactive whiteboards are used in many schools, colleges and universities as well as corporate environments. Currently two whiteboard manufacturer’s, SmartBoard and Promethean, have developed their range to include a short throw projector with built-in audio on a frame ready for wall mounting. However, at the time of writing, these do not include a microphone option.  You would need to purchase a separate wireless microphone.

Powered wall speakers

Obviously, when a microphone is used in a classroom it cannot be a wired microphone as you would have trailing wires around the classroom, so it has to be wireless, i.e. a radio microphone.   Radio mics tend to be either VHF (very high frequency) or UHF (ultra high frequency). 

Multiple wireless microphones in schools and colleges with many classrooms can get interference with cross talk.  Can you imagine sitting in a classroom discussing English and you can hear what is going on in the next classroom who are working on maths.  For information on wireless microphones please see the Microphone section in this guide.

Many schools, who use interactive voting systems, are already familiar with IR and RF, as voting systems are available in either infrared (IR) or radio frequency (RF).   The problem with IR is that it has to be line of sight, so when pupils press the button on their own handset to send their answer, if they aren’t in sight of the receiver, which may be on top of the interactive whiteboard and a tall teacher is blocking it, then it won’t work.    Thus there is a leaning by some manufacturers towards RF systems.  Teachers who use these will already be familiar with IR or RF systems.

When using radio frequency wireless microphones, there are licensing issues and these will need to be addressed.  There are a number of frequencies that can accessed without a license. 

There are two ways of licensing radio frequencies for wireless microphone use and two exceptions (at the time of writing)

• 48 hour license for temporary assignments or long term/high power outdoor use
• Fixed site license for long term, indoor, low power assignments

• License exemption frequencies
• Shared frequencies

License frequencies are co-ordinated or UHF in-band frequency:

Coordinated - means the license will specify the location and date of use and JFMG can ensure that allocated frequency is free from external interference.  For example, you can have a 48 hour licence for a two-day outdoor event.

UFH in-band frequency - the frequencies 470MHz to 854MHz are known as ‘in-band’ as they are shared on a secondary basis to TV broadcasting frequency. These frequencies correspond with TV channels 21-68.

  Licence exempt frequencies – the frequencies 863 – 865MHz are exempt from all licensing (at the time of writing). Do check manufacturer’s specification sheets to see whether their radio microphones can tune to frequencies in this range if you want to be exempt from licensing. However, only a limited number of simultaneous channels are available, typically a maximum of three. 

Shared frequencies – shared refers to a group of 14 frequencies between 854 and 862MHz (TV channel 69), and are available for use at any venue, using a shared frequency licence. This current cost of this licence is currently (at time of writing) £75 per year. These frequencies are more likely to have interference often referred to as ‘intermodulation’.

Licensing regulations do change so you will need to check that you have up to date information from the licensing regulatory body.

Whatever audio equipment is purchased for schools, then to comply with voice reinforcement and sound fields, it will need careful consideration and planning. For up to date comparison charts please visit: www.commercialsoundsystems.co.uk

Wedgwood publish an Audio guide and an Induction Loop guide, FREE from www.wedgwood-group.com