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Acoustics and sound insulation

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  1. Acoustics and sound insulation PREPARED BY MANISH KUMAR LECTURER ARCHITECTURE AT GOVT. POLY. COLLEGE FOR GIRLS PATIALA PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  2. GENERAL INTRODUCTION • Sound is generated in the air when a surface is vibrated. • The vibrating surface sets up waves of compression and rarefaction. • To understand it let us take example of tuning fork PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  3. GENERAL INTRODUCTION • I have drawn three pictures of a tuning fork to help you visualize how air molecules might look around a tuning fork. • When the tuning fork is at rest, the fork is surrounded by molecules in the air. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  4. GENERAL INTRODUCTION • As a tuning fork's prongs move apart because of a vibration. • The molecules ahead of it are crowded together. • They look like they are being pushed together. They bump each other. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  5. GENERAL INTRODUCTION • As the tuning fork's prongs come back together, it leaves a region that has fewer molecules than usual. • The region of a sound wave in which the molecules are crowded together is a compression. • The region of a sound wave in which particles are spread apart is a rarefaction. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  6. GENERAL INTRODUCTION • As a tuning fork vibrates, it causes molecules in the air to move. • The molecules bump into other molecules nearby, causing them to move. • This process continues from molecule to molecule. • The result is a series of compressions and rarefactions that make up sound waves. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  7. GENERAL INTRODUCTION • And these compression and rarefactions sets the ear drum vibrating. • The movements of ear drum are translated by the brain into sound sensation. • So, we really don't hear with our ears - we hear with our brains! PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  8. GENERAL INTRODUCTION Shape (dish type) of the outer ear is helpful in receiving sound waves. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  9. GENERAL INTRODUCTION Here's How It Works • Sound vibrations, or sound waves, are collected by the OUTER EAR. • And travel into the ear canal, where they bump up against the ear drum. • The EAR DRUM vibrates in sympathy with these sound waves. • As it vibrates, it moves a series of tiny bones in the MIDDLE EAR PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  10. GENERAL INTRODUCTION • Which carry the vibrations to a fluid-filled tube called the cochlea in the INNER EAR • The fluid inside the cochlea vibrates a series of tiny hairs called cilia, which are attached to auditory nerves. • The movement of these cilia stimulates the nerves. • And they send signals to the brain, which, in turn, processes these signals into the sounds we hear. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  11. GENERAL INTRODUCTION PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  12. Characteristics of sound • There are three characteristics of sound. • Intensity and loudness and it is measured in decibel • Frequency and pitch of sound it is measured in “Hertz" (Hz) or "cycles per second”. • Quality or timbre of sound. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  13. Intensity and loudness of sound • Intensity of the sound is defined as the amount or flow of wave energy crossing per unit time through a unit area taken perpendicular to the direction of propagation. • Intensity of sound is purely a physical quantity which can be accurately measured and is independent of the ear of the listener. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  14. Intensity and loudness of sound • Loudness of a sound corresponds to the degree of sensation depending upon the intensity of sound and sensitivity of ear drums. • It may also happen that the same listener might give different judgments about the loudness of sound of the same intensity but of different frequencies as the response of the ear is found to vary with the frequency of vibration. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  15. Frequency and pitch of sound • Frequency or pitch is defined as the number of cycle which a sounding body makes in each unit of time. • It is measure of the quality of sound. • The sensation of pitch depends upon the frequency with which the vibrations succeed one another at the ear. • Greater the frequency the higher the pitch. • And the lesser the frequency the lower the pitch. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  16. Frequency and pitch of sound • The audio range falls between 20 Hz and 20,000 Hz. This range is important because its frequencies can be detected by the human ear. • A frequency is expressed in terms of Hz(Hertz) and it determines pitch of sound source. They can be categorized as: • Low tones –sound of urban road traffic. • Mild tones –sound of piano notes. • High tones –sound of single tea kettle. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  17. Quality or timbre of sound. • The quality of sound is that characteristics which enables us to distinguish between two notes of the same pitch and loudness played on two different instruments or produced by two different voices. • It is to be noted that it is that tonal quality which enables us to recognize a large number of different sounds. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  18. The behavior of sound propagation It is affected by many things: • The speed of sound within the medium depends upon temperature of the medium ,which in turns effect the density and pressure of the medium.. • The propagation is also affected by the motion of the medium itself. • For example, sound moving through wind is further transported towards the direction of wind. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  19. The behavior of sound propagation • The viscosity of the medium also affects the motion of sound waves. • It determines the rate at which sound is attenuated. • For many media, such as air or water, attenuation due to viscosity is negligible. • Sound cannot travel through a vacume. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  20. The behavior of sound propagation • It travels much faster in solids and liquids then in air. • The velocity of sound in atmospheric air at 20 degree centigrade is 343 meter per second. • The velocity of sound in pure water is 1450 meter per second. • The velocity of sound in bricks is 4300 meter per second. • The velocity of sound in concrete is 4000 meter per second. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  21. The behavior of sound in enclosures • When the sound waves strike the surface of room three things happen • Some of the sound is reflected back in the room. • Some of the sound energy is absorbed by the surfaces and listeners of the room/hall . • And some of the sound is transmitted out of the room through vibrations of floors, walls and ceilings. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  22. The behavior of sound in enclosures • The amount of sound reflected and absorbed depends upon the different surfaces of room. • And the sound transmitted outside the room will depend upon . • The sound insulation properties of walls , floors and ceiling etc. . PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  23. Reflection of sound waves. • Reflection of sound waves is exactly the same as that of light waves. • That is angle of incidence is equal to the angle of reflection. *c REFLECTED WAVE INCIDENT WAVE *c *c REFLECTING SURFACE. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  24. Reflection of sound waves. The reflected wavefront from a flat surface are also spherical and their centre of curvature is the image of source of sound. FLAT REFLECTOR WAVE FRONT SOUND SOURCE PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  25. Reflection of sound waves. • Sound waves reflected at a convex surface are magnified and are considered bigger. • They are attenuated and therefore weaker. • So convex surface may be used with advantage to spread the sound waves throughout the room. WAVE FRONT CONVEX REFLECTOR SOUND SOURCE PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  26. Reflection of sound waves. • The sound waves reflected at a concave surface are considered smaller. • The waves are most condensed and therefore amplified. • The concave surface may be provided for concentration of reflected waves at certain points. CONCAVE REFLECTOR WAVE FRONT SOUND SOURCE PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  27. Acoustics general introduction • The scientific study of the phenomenon of sound is known as Acoustics. • Acoustics as applied to buildings is the science of sound which assures the optimum conditions for • Producing sound/speech/music • Listening of sound/speech/music • Recording /editing of sound etc. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  28. Acoustical Interaction Acoustics means to work on these three parameters and improve sound experience. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  29. Acoustical Interaction • Sound is attenuated by absorption • Historically, the primary focus of acoustics was the use of absorbing surfaces to control the reverberation times and loudness of spaces. • Redirected by reflection • Uniformly scattered by diffusion • Good architectural acoustic design requires an appropriate combination of absorptive, reflective and diffusive surfaces PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  30. Acoustics general introduction • For better acoustical results the construction and application of sound absorbents and sound reflective materials should be carefully selected and placed. • This will help in providing better quality of audio video sensations to viewers/ listeners. • Proper acoustical planning can reduce or completely eliminate defects related to sound ,which are called acoustical defects. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  31. Acoustical defects • List of acoustical defects • Reverberation. • Formations of echoes. • Sound foci. • Dead spots. • Insufficient loudness. • Exterior noises. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  32. Acoustical defects (Reverberation) • Reverberation is the persistence of sound in the enclosed space , after the source of sound has stopped. • Reverberant sound is the reflected sound , as a result of improper absorption. • Reverberation may results in confusion with the sound created next. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  33. Acoustical defects (Reverberation) • However some reverberation is essential for improving quality sound. • The time during which the sound persists is called the reverberation time of sound in the hall. • As per Prof. W .C. Sabins reverberation time ‘t’ is given by formula :- t= 0.16V /A where V=volume of room in cubic meters A= total absorbing power of all the surfaces of room/ hall. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  34. Acoustical defects (Reverberation) PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  35. Acoustical defects (Reverberation) PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  36. Reverberation time & quality of sound • Reverberation time should remain within limits as per Indian Standard Code: 2526-1963. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  37. Formation of echoes. • Echo's • Not all sound that hits matter is absorbed. Some of it is reflected. That means sound bounces off the solid matter the way a tennis ball bounces off a wall. Sound reflected back to its source is an echo. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  38. Formation of echoes. • An echo is produced when the reflected sound wave reaches the ear just when the original sound from the same source has been already heard. • Thus there is repetition of sound. • The sensation of sound persists for 1/10th of a second after the source has ceased. • Thus an echo must reach after 1/10th second of the direct sound PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  39. Formation of echoes. • Multiple echoes may be heard when a sound is reflected from a number of reflecting surfaces placed suitably. • This defect can be removed by selecting proper shape of the hall . • And by providing rough and porous interior surfaces to disperse the energy of echoes. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  40. Sound foci • Some times shape of the hall makes sound waves to concentrate in some particular areas of hall creating a sound of large quality. • These spots are called sound foci. • This defect can be removed by • Geometrical design shapes of the interior faces. • Providing highly absorbent materials on critical areas (curved spaces). PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  41. Dead spots. • This defect is the out come of formation of sound foci. • Because of high concentration of reflected sound at sound foci , there is deficiency of related sound at some other points. • These spots are known as dead spots where sound intensity is so low that it is insufficient for hearing. • This defect can be removed by suitably placing diffusers and reflectors. • Right proportions of internal spaces. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  42. Dead spots. Geometrical shape of roof helps in proper distribution of sound PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  43. External noise • External noises from vehicles , traffic engines , factories , machines etc. may enter the hall either through the openings or even through walls and other structural elements having improper sound insulation. • This defect can be removed by proper planning of the hall with respect to its surroundings and by proper sound insulation of external walls. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  44. Acoustical design of halls • The initial sound from the source should be of adequate intensity so that it can be heard throughout the hall . • For halls of big sizes suitable sound amplification system should be installed. • The sound produced should be evenly distributed so that there is no dead spots and sound foci. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  45. Acoustical design of halls • The boundary surface should be so designed that there are no echoes or near echoes. • Desired reverberation time should be achieved by proper placement of absorbents on wall. • The out side noise should be eliminated. PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  46. Physical Design Principles for halls PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  47. Physical Design Principles for halls PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  48. Physical Design Principles for halls PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  49. Physical Design Principles for halls PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

  50. Physical Design Principles for halls PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA