Room Acoustic Design

Alphacrete Acoustic Masonry

With new research into acoustics in schools it has become apparent that often classrooms have poor acoustics. As a result this can have a significant negative impact on the educational development of children. Whilst adults can make guesses at words missed, children often find it harder to do so.

Prior to 2003, Part E of the Building Regulations did not apply to schools. It now includes schools within its scope. Building Bulletin 93 aims to:

• Provide a regulatory framework for 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 those who are involved in the design of new or refurbished school buildings.

Performance standards are defined in BB93 for the following:

• Indoor ambient noise levels from external sources and building services defined on a room classification basis
• Airborne sound insulation between spaces
• Impact sound insulation of floors
• Reverberation within teaching and study spaces
• Sound absorption requirements for corridors, stairwells and entrance halls
• Speech intelligibility requirements in open plan spaces

Unfortunately classrooms throughout the UK and Ireland currently suffer from poor room acoustics. The problem can be eradicated at the source however with the use of a revolutionary Acoustic masonry block Alphacrete Acoustic.

The science behind poor acoustics.

Why are some rooms acoustically poor?
There are a number of factors to take into account when analysing the acoustics in any one room, the following play a major part in creating a poor acoustic environment.

• Too much reverberation
• Sound from other rooms penetrates the walls
• Flutter echos

What is reverberation?
Reverberation is the persistence of a sound after its source has stopped, resulting in poor speech intelligibility in rooms.

The effect of reverberation on speech.
Decreases the overall understanding of speech
Vowels interrupt the understanding of lower loudness consonants. Vowels tend to be 10-15 dB louder than consonants.
Silent intervals between syllables, sounds and words are filled with reflective energy resulting in a smearing effect of the sound.

Ways to reduce reverberation time.
In order to reduce reverberation time, you need to increase the absorption in the room. Absorption can be increased by the replacing of covering hard surfaces with softer ones to minimise the amount of reflection.

Acoustic experts have already proven that Alphacrete Acoustic blocks offer significantly better acoustic absorption than alternative products that are typically employed in similar applications. The graph illustrates this by comparing the performance of A308 Ernestone with absorption data for various products as set out in BB93 Acoustic Design of Schools.

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