Done By: Khawla Al-Shidi Supervisor: Dr. noor University Of Nizwa Collage Of Engineering & Architecture Department Of Architecture & Interior Design Sound Absorption Done By: Khawla Al-Shidi Supervisor: Dr. noor

Sound Absorption The basic problem with all of these facilities is that the surfaces are too far from the listener and/or performers to provide useful reinforcement by reflected sound energy. Instead, reflections from the boundary surfaces are heard as echoes. The basic acoustical design consists of making these surfaces sound absorbing by means of massive applications of acoustical treatment ..

Sound Absorption The acoustical materials used must have high absorption coefficients in the speech frequency range, particularly 250 to 4000 HZ. Concrete surfaces may employ thick sound-absorbing form boards that are lift in place on the underside of the concrete . Steel surfaces may employ perforated metal roof decks ,

Sound Absorption underside of the consisting of a sandwich of perforated metal on the bottom, glass fibre in the middle, and sheet metal above. Inflatable domes can employ special sound-absorbing fabrics installed to sag beneath the actual dome material . The airspace between the sound-absorbing fabric and the dome material above is necessary for efficient sound absorption. Many ,many alternatives exist for treating ceilings with sound-absorbing materials

Sound Absorption Wall surfaces are usually also treated. Hard seas may be essential in some projects for reasons other than acoustics, but upholstered seats are better, and sometimes perforated seat bottoms (which expose sound-absorbing material within the seats ) are used to control the build-up of reverberation that accrues when occupancy is low.

Sound Absorption The concept of reverberation time is somewhat meaningless in regard to such large spaces. Even with all significant areas treated efficiently, reverberation times can run to4or 5 sec because of their tremendous volume.(If room surfaces are left untreated, reverberation times as high as 10 sec have been recorded.) The important goal is to treat any potential echo-producing surface and not to aim for a particular reverberation time .

Sound Absorption A final reason for the massive application of sound- absorbing treatment is to control crowd noise. In large, untreated sports spaces, crowd noise can build-up to the point where even massive, high-level sound systems cannot communicate emergency information .With treatment, crowd noise during an exciting part of a sports event can usually be held to broadband levels of approximately 95 dB (flat) , and the sound system can be designed to override such levels without causing damage.

Cultural Events The accommodation of cultural events in these large spaces should, after proper treatment of boundary surfaces , be similar to that for outdoor facilities. Stage enclosures or concert shells are useful for symphony orchestras and choruses. Soundproof Wall

Music building Music buildings contain a variety of spaces with special room acoustics needs. Included are recital halls, large rehearsal room, ensemble rooms, music class rooms, practice rooms, among other.

Music building Musical instruments produce as much sound power in small rooms as in large auditoriums and can be uncomfortably loud. for reduced sound intensity, sound absorbing materials are used extensively in music building.

Rehearsal rooms Rehearsal rooms also require a good deal of installed sound-absorbing material for the sake of reverberation control, loudness reduction, and, in particular instances, elimination of flutter-echo paths between parallel walls. The first two of these items relate to quantity of these items relate to quantity of material, while the last relates to distribution.

Home listening rooms Small rooms can produce significant coloration and poor spatial imaging of reproduced sound if they are not treated extensively and uniformly with broadband sound absorbing material. In other words, the sound of the room itself (due to reflections and resonance) should be substantially suppressed, though not totally, and this requires large areas of effective sound- adsorbing and sound-diffusing treatments on all surfaces. Adsorptive treatment should be applied so that average coefficients in each of the room's principal axes are about the same.

Home listening rooms For accurate imaging, a listening room must be totally symmetrical about the vertical plant along the principal listening axis with respect to both treatment and geometry. in other words, the left and right playback channel should see identical sound transmission paths. Surround channels must also be given consideration with respect to loudspeaker placement and transmission.

Lecture rooms Large lecture room acoustic requirements may be equated to those of small theaters. The boundaries should be shaped for good natural reinforcement of the speaking voice, and usually this applies most particularly particularly to the ceiling.

Lecture rooms Applied sound-absorbing treatment may be useful for controlling reverberation, echo, and flutter. Likely areas to receive treatment include the ear wall, the perimeter of the ceiling, and side wall areas between seated and standing head height. The latter is especially helpful in rooms with parallel side walls. The stock solution of acoustic tile ceiling and hard walls should be avoided.