Building Utilities 3 - Lecture Notes PDF

Building Utilities 3 Ar. Sarrah Kay Dela Cruz, UAP Online and Face to Face Classes Must have proper account name on the following apps: Video Class Submission of other requirements Class Announcements Availability of Pro...

Building Utilities 3 Ar. Sarrah Kay Dela Cruz, UAP Online and Face to Face Classes Must have proper account name on the following apps: Video Class Submission of other requirements Class Announcements Availability of Professor For Questions on the course: Kindly PM me on my messenger or Email me at [email protected] Requirements Quizzes Assignments Exams (Prelims, Midterms, Finals) Research Papers Final Plate  Review on BU 2 Mechanical and Electrical Systems Building Utilities 3 About the Course COURSE DESCRIPTION The psychophysics of acoustics and lighting; its measurement, analysis, and application to Architectural discipline. COURSE OUTCOMES At the end of the course, the students should be able to: 1. Relate the knowledge gained on the different aspects of acoustics and lighting: principles, design, and application to designing space and building envelope. 2. Provide architectural design solutions to the psychological and physiological effects of sound and light on the building occupants. 3. Integrate technology in the application of lighting and acoustics in designing space and building envelope. Acoustics Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. Images: Google Image Acoustics acoustic borrowed from Medieval Latin acousticus, acūsticus, borrowed from Greek akoustikós, from akoustós "heard, audible" verbal adjective of akoúein "to hear," Images: Google Image Sound The sensation stimulated in the organs of hearing by mechanical radiant energy transmitted as longitudinal pressure waves through the air or other medium. The word Sound is often used to describe two different things: 1. An auditory sensation 2. The disturbance in a medium that can cause this sensation Source: Visual Dictionary of Architecture, DK Ching Types of Sound Wanted Sound (speech, music) – heard properly; considered desirable Unwanted Sound (noise) – annoyance; not desired or objectionable Characteristics of Sound - Audible (between 20Hz and 20000 Hz) - Inaudible (sounds below 20Hz and over 20000 Hz) Images: Google Image Sound Waves Pressure fluctuations in the air that are heard when an acoustic wave passes by. They are usually caused by objects in the air that quickly change position or a stream of air that quickly changes position. Sound escapes away from the sound source as an expanding spherical wave that travels at the speed of 1130 feet per second, traveling about 1 1/8th of a foot each one thousandths of a second (millisecond). Images: Google Image Frequency The units of frequency are called hertz (Hz). Humans with normal hearing can hear sounds between 20 Hz and 20,000 Hz. Frequency SOUND PRESSURE Sound Level The measure of the strength of sound. Units are decibels (dB) and usually measured with a dB meter. The threshold of quiet sound is zero dB and the onset of painful sound is 100 dB. Conversations are at 50 dB, whispers at 30 dB and shouting is 70 dB. When the sound strength of something doubles, it increases by 3 dB, or halved, it drops by 3 dB. Images: Google Image Loudness The apparent strength of the sound to the listener. A change in 1 dB is just barely noticed as a change in loudness. Something twice as loud is actually 10 dB stronger, (10 times stronger). Something half as loud is 10 dB weaker, (1/10th as strong). Images: Google Image Decay Decay Rate The dying out of sound. Usually The time (in seconds) it takes for referring to the steady decline in reverberation to change from very the loudness of the loud to imperceptibly quiet, a total sound level difference of 60 dB. For reverberation. a living room the RT-60 might be 1 second but in a gym, it might be 4 seconds. Images: Google Image Noise/ Background Noise The unwanted, undesirable and usually interfering sounds present in a listening space, typically due to an air conditioner or other conversations. Noise Floor The strength of the background noise, measured in dB. It is difficult to understand what is being said in a room with a high noise floor. Signal-to-Noise Ratio (S/N) The difference in sound level (dB) between the desired sound and the noise floor.  NRC Rating (Noise Reduction Coefficient) A rating for absorption. It gives the % efficiency for a surface to absorb sound. If a surface is 30% absorptive, then only 70% of the incident sound is reflected back into the room. Images: Google Image  Intelligibility A measure of the clarity of sound based on the comprehension of the message being conveyed by sound. A "cat, bat, tat, rat... type of recognition test. The conversational version of Articulation. Images: Google Image Sound Spectrum The sound level measured at different frequencies. Most tones are composed of more than one frequency, a combination of frequencies, as in a musical chord. The sound spectrum would measure the strength of each frequency and display that graph as a plot of Sound Level vs. Frequency, also known as a sound spectrum. The "color" of sound is used as emphasis in the spectrum. Architectural Acoustics 23 Transmission, Reflection and Absorption of Sound Similar to a light wave, when a sound wave encounters an object, one of three things can happen: 1. Transmission – the sound wave travels through the object. 2. Reflection – the sound wave bounces off the object, often creating an echo. 3. Absorption – the sound wave is ‘trapped’ by the object, where its energy is transformed into a small amount of heat. Usually a combination of all three processes occurs, with the proportion of each depending on the composition of the object and the frequency of the sound wave. Hard surfaces reflect sound more than soft surfaces. Thicker or more dense objects absorb more sound; thinner or less dense objects transmit more sound. Low frequency sounds are more likely to be transmitted; high frequency sounds are more likely to be reflected or absorbed 24 Direct Sound The part of a sound wave that travels directly along the line of sight path between the speaker or sound source and the listener. The dry or actual sound. 25 Reflections Sound waves that strike a surface and bounce off are reflected sounds. They bounce off the wall, changing directions but keeping the same angle off the wall as they had when they approached the wall. 26 Early Reflections Reflections that are heard within 1/20 of a second of the direct sound are called early reflections. Early reflections cannot be distinguished from direct signals, they merge with the direct sound to form one composite sound. This combining effect can cause the sound of the direct signal to change in tonal characteristics and apparent direction. 27 Late Reflections (Echo) A distinct reflection that arrives at the listener later than 1/20th of a second after the direct sound is heard. The listener can identify from where an echo comes. An echo does not change the tonal characteristics of the direct sound. 28 Flutter Echo This type of echo is most easily heard as one claps their hands out in front of them, while standing in a hallway. The sound "zings" and it's tone depends on how many times a second the reflection passes by the listener's head. In a hall 8' wide, the clap will expand out, hit the wall and return 143 times a second and the zing will sound like a 143 Hz buzzy tone. Not a real sound, just a pseudo-tone. 29  https://youtu.be/KGGNvJGaJ0U Flutter Echo 30 Reverberation For sound in a large room, reverberation begins at about 1/5 second following the direct sound. It is due to the accumulation of many reflections, compounding one upon the other, so much that the sound no longer seems composed of echoes but rather just a sound of noise, a din of chaos that has no discrete direction and no discrete timing. 31 Diffusion Reflections off of a non flat surface that causes the sound wave to become more quickly disorganized than if off a flat surface is a diffusive surface. Diffusion decreases the time it takes for echoes to become converted to reverberation. The beautiful gothic churches of the old world have very diffusive or sound scattering surfaces. That is part of the sonic beauty of those spaces. 32 ROOM ACOUSTICS https://youtu.be/JPYt10zrclQ?si=KrI8nu2xyetrbxu6 33 End of Presentation 34