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MODULE 1 Acoustics LESSON 3: Importance of acoustics Architects need to consider aside from aesthetic:  health and safety  productivity  comfort & human factors functionality PRODUCTIVITY  Hearing loss is one of the leading disability in the world  Hearing loss is one of th...

MODULE 1 Acoustics LESSON 3: Importance of acoustics Architects need to consider aside from aesthetic:  health and safety  productivity  comfort & human factors functionality PRODUCTIVITY  Hearing loss is one of the leading disability in the world  Hearing loss is one of the most common occupational hazard.....with nearly more than 100million workers exposed to potentially hazardous noise levels on the job Numerous studies demonstrate that noise is the #1 inhibitor to productivity Unsafe levels of sounds can be, for example, exposure to in excess of 85 decibels (dB) for eight hours or 100dB for 15 minutes (WHO, Feb 2015) Decibel Range Chart (SAFE) UST COLLEGE OF ARCHITECTURE BU3 1  MODULE 1  Some 1.1 billion teenagers and young adults are at risk of hearing loss due to the unsafe use of personal audio devices, including smartphones, and exposure to damaging levels of sound at noisy entertainment venues such as nightclubs, bars and sporting events (WHO, Feb 2015)  Excessive noise exposure can cause “Tinnitus” (characterized by a constant ringing, hissing or other sound in the ears or head when no external sound is present) HEALTH & SAFETY Noise had been linked to a number of ailments other than hearing loss, such as:  ULCERS STRESS HEADACHES  DIGESTIVE ISSUES HIGH BLOOD PRESSURE HEART PROBLEMS  RESPIRATORY AILMENTS COMFORT  Noise is frequently the cause of irritating, uncomfortable or even oppressive environments.  Painfully noisy restaurant Conference rooms with annoying reflections  Noise is frequently the cause of irritating, uncomfortable or even oppressive environments.  Cafeterias with overwhelming reverberation  Lecture halls where its difficult to understand speech FUNCTIONALITY Imagine...you’ve spent months on a project and its finally completed. You’re excited, it looks great....but the client reacts... “It’s beautiful.... but we can’t use this.” Owner of a newly constructed reception hall’s reaction to an acoustically unusable space. https://www.labanquets.com/galleries/legacy/Modern%20Venue%20Le gacy%20Ballroom%20L%20A%20Wedding%20Venue%20(14).jpg UST COLLEGE OF ARCHITECTURE BU3 2  MODULE 1 Spaces wherein “QUIET” is a necessity  Libraries  Museums  Health Care facilities Spaces wherein “UNDERSTANDING OF SPEECH” are vital  Classrooms  Boardrooms  Lecture Halls  Courtrooms Spaces that requires “BUZZ” isn’t overwhelming  Restaurants  Lobbies  Food Courts  Malls Spaces that ensure “PUBLIC ANNOUNCEMENTS” audibility  Airports  EducationalFacilities  Government Facilities  Public Spaces Spaces wherein “SPEECH PRIVACY “is a key  Open office  Call centers  Meeting areas Spaces wherein “MUSIC ENHANCEMENT” is crucial UST COLLEGE OF ARCHITECTURE BU3 3  MODULE 1  Recording studios  Concert halls  Practice rooms  Performance spaces Spaces wherein “CONFIDENTIALITY” is essential  Doctor’s office  Human resources  Police facilities  Counselling office Spaces wherein “SPEECH & MUSIC” must be considered  Worship centers  Theatres Clubhouses  Multipurpose room “Whether you are working on a recording studio, concert halls, lobby, office, etc. You need to consider “acoustics” As architects, we need to consider acoustics during the “Design Development Stage,” in order to:  Reduce costs  Don’t sacrifice aesthetics Limit your liability Protect your client UST COLLEGE OF ARCHITECTURE BU3 4  MODULE 1 LESSON 4: Fundamentals of Acoustics Revised and Prepared by: Ar. Aurora Amand a V. Fernandez Original lecture by: Ar. Rino Domingo Fernandez) FUAP UST COLLEGE OF ARCHITECTURE BU3 5  MODULE 1 UST COLLEGE OF ARCHITECTURE BU3 6  MODULE 1 UST COLLEGE OF ARCHITECTURE BU3 7  MODULE 1 UST COLLEGE OF ARCHITECTURE BU3 8  MODULE 1 UST COLLEGE OF ARCHITECTURE BU3 9  MODULE 1 UST COLLEGE OF ARCHITECTURE BU3 10  ACOUSTICS HANDOUT AR1129 BU3 1 ARCHITECTURAL ACOUSTICS ACOUSTICS 1. Defined as the science of sound, including the;  Generation  Transmission, and  Effects of sound waves. 2. The totality of those characteristics of a room which affects an individual’s perception, and his judgment of speech and music produced in the room. These characteristics includes the ff:  Size and shape of elements on the walls or ceiling that scatters sound  The amount of absorption  The noise level within the room  Reverberation time of sound waves within the room Acoustical situation can be described by three parts;  Source  Path, and  Receiver Sound sources can be made louder or quieter, for example strategic placement of reflecting surfaces near the speaker in lecture rooms, churches and auditoriums can reinforce and evenly distribute sound to all listeners. The path:  Air  Earth  Building materials etc. These can be made to transmit more or less sound, and when required, building components can be designed to interrupt the sound path, thereby providing satisfactory sound isolation and privacy. The receiver are the users, usually are affected by these two parts. Sound Defined as the vibration in an elastic medium such as;  Air  Water  Most building materials, and AR ROEL J FIECAS UST COLLEGE OF ARCHITECTURE  ACOUSTICS HANDOUT AR1129 BU3 2  The earth An elastic medium is a condition which returns to its normal state after a force is removed. Sound energy progresses rapidly, producing extremely small changes in atmospheric pressure, and can travel great distances. Pressure is a force per unit area. This force in elastic medium create waves as it travels through a medium. Waves To most people, “wave’’ conjures up a picture of water waves moving across a lake, or perhaps of a flag undulating in the breeze. These are called periodic waves, in which motions are repeated at regular intervals. The key word in discussing wave is simply a “disturbance”. In water waves, it is the change of positions of molecules, that is the disturbance; the surface rises and falls. In sound waves, we can consider changes in pressure to be the disturbance. In general, wave can be defined as the propagation of disturbance. A wave is composed of alternating compression and rarefaction which are detected by a receiver (human ear) as changes in pressure, hence sound waves. Basic Sound Wave Components and Properties: 1. Wavelength of a sound wave is the distance between two successive compressions or the distance the wave travels in one cycle. The distance between adjacent regions where identical conditions of particle displacement occur. To find the wavelength of sound in air at a specific frequency the formula is: λ= V/f where; λ=wavelength V=velocity f=frequency 2. Amplitude of a sound wave is proportional to the maximum distance a vibrating particle is displaced from rest. It is the level of energy of the intensity of sound at a given unit area. 3. Frequency is the rate of repetition of a periodic event. It is determined by the number of times per second of a given molecule of air vibrates about its neutral position. The unit of frequency is the Hertz (Hz). Frequency of sounds in Hertz (Hz) considered in acoustical design are in: 125 250 500 1000 2000 4000 4. Velocity of Sound is the rate at which vibrations propagate through the medium. It is the distance a certain frequency of waves travel in one second. As in a 1000 Hz sound frequency, the AR ROEL J FIECAS UST COLLEGE OF ARCHITECTURE  ACOUSTICS HANDOUT AR1129 BU3 3 distance 1000 wavelength travels in a second is the velocity. Sound travels at a velocity that depends primarily on the elasticity and density of the medium. In air, at normal temperature and atmospheric pressure, it is approximately 1130 ft./sec. or almost 800 mi/sec. This is extremely slow when compared to the velocity of light =186,000 miles/sec. However, sound may travel at a very fast 16,000 ft./s along steel pipes and duct walls. 5. Sound Pressure is sound force per unit area, and is usually measured in Micropascals (μPa), where 1 pascal is the pressure resulting from a force of one Newton exerted over an area of one square meter. Pressure can also be defined in terms of force: p=F/A where; p=pressure, F=force, and A=area 6. Sound Intensity is defined as the acoustical power per unit area in the direction of propagation measured in units w/m2. Threshold of Hearing is the range of sound energy that the human ears can detect as sound. The minimum sound is being 1x10 -12 w/m2 or 0dB and the maximum 120dB. Conversion of Intensity to Intensity Level expressed by the Formula; SIL=10 log I/I0 Where: IL = intensity level in decibel (dB) I = intensity of sound w/m2 TO = base intensity in w/m2 min -12 Threshold hearing (1X10 w/m2) Min sound level = 0 db = Ixl0-12 w/m2 Max sound level = 120db = IxlO-16 w/m2 Library = 20db Street noise = 80db Aircraft set = 120db 7. Sound Intensity Level and Sound Pressure Level The sound levels to which most mammals are sensitive extend over many orders of magnitude and, for this reason, it is convenient to use a logarithmic scale when measuring sound. Both sound pressure and sound intensity can be expressed as ratios of a measured level and a reference level, this is the decibel. Sound intensity level (SIL) and sound pressure level (SPL) are both measured in decibels (dB). SIL=10 log I/I0 where: I=measured intensity and I0= reference (base)intensity, 1x10-12 w/m2. SPL=20 log P/P0 where; P=sound pressure and P0=reference (base) pressure. AR ROEL J FIECAS UST COLLEGE OF ARCHITECTURE  ACOUSTICS HANDOUT AR1129 BU3 4 8. Decibel is a dimensionless measurements used for expressing SIL and SPL based on logarithmic scale. The decibel is 10 times the log of the ratio of two intensities and 20 times the log of the ratio of two pressures. Because decibel implies a ratio of two values and therefore a dimensionless measurements. Because sound ‘loudness” varies exponentially, we will have to normally deal with a lot of zeros when doing computations involving the parameters of sound and we have to multiply numbers rather than simply adding and subtracting them. Therefore it is more appropriate to adopt a simpler system. 9. Pure Tone is vibration produced at a single frequency. Symphonic sound consists of numerous tones at different frequencies and pressures is called Harmonics. 10. Phase is a property of sound which is less directly related to how sound is heard. Phase is important in describing how complex sounds can be constructed from the simple sinusoidal waves. An example is a set of two sound waves with the same frequency and amplitude- only their alignment with respect to time differs. Sound Propagation One of the more popular model used to describe the propagation of sound through a medium is the source, path, receiver model. The basic parameters of this model related to the perception of loudness are;  Source: source level (SL)  Path: transmission loss (TL), ambient noise level (NL)  Receiver; signal to noise ratio (SNR), received level (RL), detection threshold (DT) A simple definition of sound propagation is: RL=SL-TL Where; TL= 10 log IL @ 1 m/ IL @ r meters away from source (assume spherical spreading) Inverse Square Law The sound intensity is inversely proportional to the square of its distance traveled (assume spherical spreading). A simple definition of this principle can be expressed by: I=W/4πd2 Where; I = sound intensity in W/m2 W= sound energy in watt d = distance the sound traveled in meters (radius of spherical spreading, hence, 4πd2 to be the surface area the sphere at radius d) Free Field  condition of sound that occurs outdoor in an open field with no sound reflections.  sound level drops 6dB for every doubling of distance for sound traveling spherically. AR ROEL J FIECAS UST COLLEGE OF ARCHITECTURE  ACOUSTICS HANDOUT AR1129 BU3 5  sound that travels along a linear path drops only 3dB for each doubling of sound. Reverberant Sound  sound condition inside the room with reflected sound from interior surfaces.  no significant drop within 5f+.  noise production is achieved through room absorption. Free Field Free field conditions occur when sounds waves are free from influence of reflective surfaces (e.q. open areas, outdoors, anechoic rooms) under the free field conditions, sound energy from the point sources (e.g. warning siren, truck, exhaust) spreads spherically and drops of 6db for each doubling of distance from the source. Line sources of vehicular traffic consist of successive point source, which reinforce each other. Sound energy from line sources spreads cylindrically not spherically and drops off only 3db for each doubling of distance. Reverberant Field Indoors sound energy drops off free field conditions only near the source (usually