What is noise?<br />Noise can be a very Loud sound<br />Low-level sound but annoying<br />
Loud Noise in Hong Kong<br />The main concern of noise :Traffic Noise<br />It affects more than one million people<br />655 roads generate noise greater than 70 dB<br /> But only 101 of these roads applied barriers<br />
What can we do personally?<br />Choose some good sound insulating materials to build your flat.<br />Today, we are going to test which materials (commonly seen in our daily lives) are good at insulating sound !<br />
Sound Insulation Experiment<br />Objective <br />To compare the sound insulation ‘s effectiveness of different materials under different frequencies in term of Sound Reduction Index(R) and Transmitted coefficient (T).<br />
Materials to be tested…<br />(1)the Expandable Polystyrene (EPS) foam<br />(2)stainless steel<br />(3)wood<br />(4)A4 paper<br />
What is sound??<br />Sound is a mechanical wave <br /><ul><li>also a kind of longitudinal wave which does not have Polarization(偏震)</li></ul>produced by vibrations of objects<br />require medium for propagation<br /> example: air, water<br />cannot travel in vacuum<br />
Where the sound from?<br />Can be found easily in our daily life<br />For example,<br />Musical instrument<br />Car<br />Talking<br />Aircraft take-off<br />
Sound Insulation<br />Insulate the sound we don’t want to hear<br />The ability for the material to reduce the sound energy transmitted into an adjoining air space.<br />Type of sound insulation:<br />Airborne Sound Insulation<br />Impact Sound Insulation<br />
Airborne Sound Insulation<br />the insulation against noise originating in air, e.g. voices, music, motor traffic, wind.<br />Impact Sound Insulation<br />the insulation against noise originating directly on a structure by blows or vibration <br />
Insulated the sound by mean of …<br />reflection<br />absorption<br />Sound would reflect at the surface of material so that only a part of sound energy will be transmitted. <br />Also, material will absorbs the sound energy and dissipates in form of heat making the reduction of transmission of sound.<br />result in reduction in sound level<br />
Decibel meter<br />using a decibel meter, we can measure the sound level (in dB) of different sound source. <br />sound level (L)<br /> L = 10 log10 [ I/I0 ]…………………(1)<br />sound reduction index (R):<br /> R = 10 log10 [ 1 / T ] (dB)…………(2)<br /> T: Transmitted sound energy / Incident sound energy<br />
<ul><li>Dimension of the shoe box = 29cm x 19cm x11cm = 6061cm3
Area of the opened part = 19cm x 11cm = 209cm2</li></li></ul><li><ul><li>Frequencies chosen:
Materials used:</li></li></ul><li>Sound Insulation Experiment<br />Procedure:<br />Cut out one side of the shoe box and place the cloths inside the box.<br />Set up the apparatus following the sequence from A to D as shown in Fig. 1.1.<br />
3. Turn on the speaker and generate a frequency of 125Hz (f1).<br />4. Measure the sound level (L0) using the sound meter and record it in Table 1.1.<br />5. Put the Expandable Polystyrene (EPS) foam (material 1) in front of the shoe box to cover the opened part of the box.<br />6. Measure the sound level (L1) for three times using the sound meter and record them in Table 1.1.<br />
7. Repeat steps 2 to 5 for the remaining measurements using other frequency and material.<br />8. Calculate the average sound level (Laverage= (L1+L2+L3)/3), Sound Reduction Index (R) and transmitted coefficient (T) for different material under different frequency using equation (2).<br />9. Draw bar charts to show the relation between R/T and different frequencies for different materials.<br />
Impact sound can transmit through the ground to the box due to the vibration of speaker.
For the sound transmitted through the material , the sound wave can be reflected inside the shoe box, which may be noise, and it may affect the reading.</li></li></ul><li><ul><li>The background noise may not be constant though out the experiment.
Maximum possible error of the measurement = 0.05dB x 2 = 0.1dB</li></li></ul><li>In Our Experiment<br />Conclusion:<br /><ul><li>The greater the R, the greater the Sound Reduction Level is. </li></ul>( R↑->Reduction Level↑)<br /><ul><li>The smaller the T, the greater the Sound Reduction Level is.</li></ul>( T↓-> Reduction Level↑)<br /><ul><li>The most effective sound insulation material :</li></ul>Steel board (2mm)<br /><ul><li>The least effective sound insulation material :</li></ul>EPS foam (18mm), A4 paper - 50pcs (5mm)<br />
Some Professional Insulation Materials<br />features & benefits:<br /><ul><li>high performance soundproofing material for reducing airborne noise.
may be used behind drywall in wall and ceiling assemblies or sandwiched between existing and new drywall.
use in flooring systems to increase sound transmission class.
used for both residential and commercial soundproofing applications.</li></ul>QUIET BARRIER® HDSuperior soundproofing material for blocking noise for residential and commercial use.<br />
features & benefits:<br /><ul><li>cost-effective, low-profile sound blocking barrier
designed to reduce noise transmission in wall, floor & ceiling assemblies
Measures of soundproofing at home<br />Paints the wall with latex paints<br /><ul><li>reduce sound</li></ul>Install carpets on the floor<br /><ul><li>absorb sound</li></ul>Install drapes or shutters on the windows<br /><ul><li>absorb sound</li></ul>Soft furniture<br /><ul><li>dampen sound waves</li></li></ul><li>Solid doors<br />keep sound out of individual rooms<br />install a clear window film<br />provide a soundproofing buffer<br />rearrange furniture<br />E.g. place a filled bookshelf <br /> against a particularly noisy wall<br />decorate room with rough <br /> surface finishings<br />effect multiple distortion to the propagation of the wave<br />