- Samantha Hathway
Reverberation is an important issue within room acoustics and is well known to affect both speech intelligibility and the music quality experienced by listeners. But there are various other effects that should be considered, but which are commonly neglected.
Reverberation affects the level of sound within a particular room – often with far-reaching effects. Sound levels generated by a source in a reverberant room will be greater than the same sound in a much more ‘dead’ room. Sound breaking-into the room from an adjacent area, or ventilation noise carried into the room via ductwork, will be affected in the same way. The effect of reverberation on sound level can also affect privacy within the space, as the reverberation will cause the sound to ‘carry’ further, potentially breaking-out into adjacent areas.
Being such an important principle, reverberation requires detailed consideration in most types of building. In concert halls and theatres, room acoustics is obviously paramount, as the effect of bad acoustics can have dire commercial consequences. In offices, controlling reverberation in open plan areas is critical to maintaining privacy, while in densely-occupied call centre arrangements, minimising reverberation levels will promote a more pleasant working environment. On an aesthetic note, the acoustics of large entrance areas and impressive atria are vital in order to provide an environment that is pleasing to both the eye and the ear.
In educational buildings, limiting reverberation in teaching areas is critical to allow clear communication between the teacher and students, as well as between students. To achieve this, designers are provided with clear performance standards in Building Bulletin 93 “Acoustic Design of Schools”, which is enforced by Part E of the Building Regulations.
Part E also includes reverberation criteria for the common parts of residential buildings and hotels, which are intended to reduce reverberation (and hence noise levels) via acoustic treatments in these areas, thus reducing the level of noise that is transmitted to adjacent apartments or hotel bedrooms.
In buildings of all kinds, a plant or equipment room may be a further source of noise break-out. Even though the machinery itself may be acoustically treated and the surrounding walls and floors built to high standards, the level of reverberation in the plantroom itself can represent the difference between inaudibility and complaints from occupiers of nearby rooms.
"It’s clear that reverberation is an important issue in many building types and has many significant implications too. So how can the phenomenon be considered and accounted for?"
Just as a ball will bounce less off a soft wall, acoustically ‘soft’ finishes have a similar effect on sound. When a sound is emitted, it begins to ‘bounce’ around the room. Each time the sound impacts on something in the room - whether a wall, floor, table, chair or a human being - a certain amount of its energy is absorbed. So the more soft finishes there are, the less reverberation there will be.
The geometry of the room also affects how sound bounces around. auricl uses sophisticated acoustic modelling software to assist with room design and material specification, allowing the optimum arrangement of the room, its surface finishes and furniture to be determined before construction has even begun.
Auralisation allows designers and clients to actually experience different environments through the use of audio demonstrations, so they can join in the process and decide how they want a particular room to sound.
Acoustic treatments have historically been unpopular with designers, who are understandably protective of their design concept. But compromises can be explored using modern materials. For example, many perforated plasterboard products with an acoustic backing are now available, which are suitable for walls or ceilings and provide acoustic absorption whilst emulating the look of traditional plasterboard. These products are available in a virtually endless array of perforation patterns, providing maximum design flexibility.
Recent breakthroughs in technology mean that fabric-covered foam acoustic panels can now be printed with photographs, images and patterns. This enables wall-mounted acoustic treatments to be incorporated into the décor, making a virtue out of a necessity.
Such seemingly simple solutions can make all the different between a noisily disorienting environment and an attractive and welcoming space where the acoustic conditions make a positive contribution to the user experience.
And involving Auricl's skills, experience and acoustic modelling expertise will ensure that your project is both aesthetically and acoustically pleasing.