The pinta Acoustics Primer - Brochure

A BRIEF INTRODUCTION TO THE WORLD OF ACOUSTICSThe pinta Acoustics Primer[2/16]WHAT ARE THE BASIC PRINCIPLES OF ACOUSTICS IN CONSTRUCTION AND ARCHITECTURE? WHICH STANDARDS AND GUIDELINES ARE RELEVANT TO ROOM ACOUSTICS? HOW DOES SOUND ABSORP-TION AND REFLECTION WORK? THE PINTA ACOUS-TICS PRIMER ANSWERS ALL THESE AND MANY OTHER QUESTIONS. A short definition of acousticsThe word “acoustic” comes from the Greek (a???e??), which means “able to be heard”. Acoustics is the sci-ence of sound and its propagation. As a branch of physics, acoustics describes wave phenomena that occur upon the propagation of small pressure fluctua-tions. Sound waves can only occur in solid, liquid and gaseous media – for example in structures, water or in air. In a vibration-free vacuum there can be no sound.Areas of acousticsThe study of sound propagation is divided into many different areas. The most important areas within the field of construction and architecture are: building and room acoustics and technical sound insulation.BUILDING ACOUSTICSBuilding acoustics are concerned with the effects of structural conditions on the propagation of sound between the rooms of a building and between room interiors and the outside world. Sub-areas of building acoustics are: Airborne sound insulation Impact sound insulation Sound insulation from technical equipment Structure-borne noiseWhere does noise come from?>>Acoustics defined Key concepts in room acoustics and sound insulationAreas of acousticsPage 2 Page 2 Page 3 Acoustics Primer[3/16]ROOM ACOUSTICSRoom acoustics are concerned with how the struc-tural conditions of a room affect the noise phenomena occurring inside it. The resulting findings are very im-portant when it comes to combating noise. In addition, the room acoustics must take into account the charac-teristics of human hearing, the special nature speech perception, subjective hearing habits and also musical aesthetics.TECHNICAL SOUND INSULATION Technical sound insulation deals with noises produced by machinery and equipment.pinta acoustic gmbh is concerned with room acoustics and technical sound insulation. Important concepts in room acoustics and sound insulationRoom noise: Noise in a closed room which has already been reflected several times by the time it reaches the place where it is heard or measured.Free-field noise: The terms “free field” or “direct field” refer to a situation in which sound is not reflected at all. Free-field conditions are only found in nature for example where new snow prevents sound from being reflected from the ground. Free-field conditions can be created artificially in non-reverberating rooms. They play an important role in acoustic measurements and hearing tests, because the results in a free-field envi-ronment are only influenced by sound from the noise source and not by reflections from the room.Room noiseFree-field noiseImportant technical standards and guide-linesSound absorbers for room acoustics and sound insulationOther important tech-nical terms Page 4 Page 7 Page 8[4/16]Sound absorption and reflection: We speak of sound absorption when a sound wave meets a soft, elastic or porous body and is wholly or partially absorbed. When this happens, sound energy is converted into heat. When a sound wave hits a hard object and is thrown back, the result is a sound reflection.Sound pressure level L P: A sound field can be quanti-tatively described through measurements. The sound pressure level is the characteristic most often mea-sured in practice. It describes the ratio of the sound pressure of an acoustic event to a reference value which roughly corresponds to the threshold of human hearing. Where the sound is able to propagate freely, the sound pressure level decreases with increasing distance from the sound source. However, if it occurs inside a room, beyond a certain distance it is more or less independent of location. This is due to reflections Room 1WallAbsorptionW1ReflectionWreflW2W3Room 2Transmission(flanking paths)Transmission(main path)DissipationWdisWabs} W2 + W3and inter-reflections on the room surfaces which cre-ate a diffuse sound field. How high the sound pressure level is depends on whether reflections occur.Important technical standards and guidelinesFOR ROOM ACOUSTICSDIN EN ISO 18041: acoustic quality (for definition see “Other important technical terms”) in small to medium-sized rooms (May 2004). This guideline distinguishes between premises of group A and B:Group A premises(medium and long distance acoustic quality) Conference rooms Courtrooms, council chambers and ballrooms Teaching rooms Seminar rooms Lecture halls Meeting rooms Interaction rooms Group rooms in kindergartens and day nurseries Old people’s day care centers Church halls Sports halls and swimming bathsAcoustics defined Key concepts in room acoustics and sound insulationAreas of acousticsPage 2 Page 2 Page 3Important technical standards and guide-linesSound absorbers for room acoustics and sound insulationOther important tech-nical terms Page 4 Page 7 Page 8Did you know that ...... sound waves are four times faster in water than in air? Sound propagates in water at a speed of 5,340 km/h. This is about the speed of the V2 rocket – the world's first long-range ballistic missile – designed by Wernher von Braun in World War II.VDI guideline 2569: Sound insulation and acoustic design in the office (January 1990)Comparison of requirements for a 50 m² office without suspended ceiling:FOR TECHNICAL SOUND INSULATIONDIN EN ISO 354: Measurement of sound absorption in a reverberation room (December 2003)DIN EN ISO 3382: Measurement of the reverberation time of rooms with reference to other acoustical pa-rameters (March 2003)DIN EN ISO 11 654: Sound absorbers for use in build-ings; rating of sound absorption (July 1997)[6/16]Acoustics defined Key concepts in room acoustics and sound insulationAreas of acousticsPage 2 Page 2 Page 3Group B premises(acoustic quality over short distances) Sales premises Restaurants, canteens Public areas for public transport Ticket counters, bank counters, call centers Lawyers’ and doctors’ consulting rooms Municipal offices Operating rooms, treatment and rehabilitation rooms, sick rooms Public areas Public access areas Reading rooms, lending desks in libraries, lending libraries Staircases, foyers, heavily frequented exhibition roomsDIN 18041 stipulates for group B premises:Room typeSales premises, work rooms, call centers, reading rooms in libraries 0.9*Multi-person or open-plan offices with office machines,Banking and ticket halls, municipal offices, operating rooms, sick-rooms, lending desks in libraries, lending libraries0.7*Single offices, consulting rooms, treatment and rehabilitation rooms, rest rooms, restaurants, dining rooms, canteenswith an area greater than 50 m0.5*Staircases, foyers, exhibition rooms, public access areas (halls and anterooms) which are heavily frequented and public areas for public transport 0.2** Required 100 % absorption area as multiple of floor area(for room height 2.5 m).Example for group B: A 50 m² multi-person office there-fore needs absorption area of 50 x 0.7 = 35 m². The reverberation time is set to 0.58 seconds. A (m²)403020100ToleranceVDI2569(1990)DIN18041(2004)Reality only with carpethighmediumlowfrequent[7/16]Important technical standards and guide-linesSound absorbers for room acoustics and sound insulationOther important tech-nical terms Page 4 Page 7 Page 8Acoustics PrimerSound absorbers for room acoustics and sound insulationFor the attenuation of airborne noise, we distinguish be-tween different type of sound absorbers.Porous sound absorbers: With porous sound absorbers, sound energy is converted into thermal energy through friction of the air particles in the pores. This demands adequate porosity and optimized flow resistance.Plate oscillator: With this type of absorber, the sound wave causes a plate to vibrate. In this way the sound energy is converted into kinetic energy.Combined absorber: By using a combination of conven-tional plate oscillators and porous absorbers, a far wider frequency range can be covered: Not only medium and high frequencies, but also low frequencies can be covered. ARRANGEMENT OF ABSORBERS IN THE ROOMWhen arranging sound absorbers in the room, it is im-portant to ensure that beneficial reflection surfaces are preserved.THE DIFFERENT CLASSES OF ABSORBERThe classification system is designed primarily for wide-band noises. The single value aW (rated sound ab-sorption coefficient, for definition see “Other important technical terms”) is used to define the sound absorber class according to DIN EN ISO 11654.Sound absorber class aw valuesA 0.90; 0.95; 1.00B 0.80; 0.95C 0.60; 0.65; 0.70; 0.75D 0.30; 0.35; 0.40; 0.45; 0.50; 0.55E 0.25; 0.20; 0.15Unclassified 0.10; 0.05; 0.00A: inappropriate absorber arrangement, because beneficial reflection surfaces become ineffective.B, C: appropriate absorber arrangement, because beneficial reflection surfaces remain effective.A B C[8/16]Acoustics defined Key concepts in room acoustics and sound insulationAreas of acousticsPage 2 Page 2 Page 3Other important technical terms (A–Z)Equivalent sound absorption area A: This term refers to an imaginary surface with total sound absorption (a = 1), which would absorb the same proportion of the sound energy as the entire surface of a material, or a room or of people and objects. The equivalent sound absorption area A of a room can be calculated from the individual partial areas Si with known sound ab-sorption coefficients a i and the sound absorption of the objects or people inside the room.Frequency f: This means the number of air vibrations per second of an acoustic event. The sound propaga-tion corresponds to an air pressure fluctuation. Low frequencies involve a small number of slow vibrations; high frequencies on the other hand involve a lot of rapid vibrations.Important frequencies in acousticsRange of hearingMusicSpeechRoom acousticsBuilding acousticsTechnical noise controlInfrasound,vibrationsUltrasound,hypersound1 10 100 1 k 10 k 100 k16 20 k16 k8 k6363 4 k5 k10 k50f (Hz)706050403063 125 250 500 1,000 2,000 4,000 8,000Male voice normal voice loudness loud voice Female voice normal voice loudness loud voice VoiceVowels Voice articulationConsonantsvoiced unvoicedmale femalePitchFrequency (Hz)Third octave levelImportant technical standards and guide-linesSound absorbers for room acoustics and sound insulationOther important tech-nical terms Page 4 Page 7 Page 8Did you know that ...... even in ancient times, it was realized that sound was caused by vibrations of solid bodies? Looking at the design of the Theater of Dionysus on the Athenian Acropolis, it is clear that the ancient Greeks had a basic knowledge of natural acoustics.[10/16]Acoustic quality: Acoustic quality means the suitabili-ty of a room for particular types of sound. The acoustic quality of a room refers in particular to the communi-cation of speech and musical performances to those parts of the room which are intended to be occupied by people. It is influenced mainly by the room’s geometry, the choice and arrangement of sound-absorbing and sound-reflecting surfaces, the reverberation time and the total background noise level.Reverberation time TN : The reverberation time TN is how long it takes for the sound pressure level in a room to fall by 60 decibels after the sound source is turned off. For practical reasons, it is usual to measure the time taken for a drop of only 30 decibels. The reverberation time of a room can be calculated from the sound absorption coefficients of surfaces and objects:T = 0.163 · V/A “Sabineformula”V = Volume of roomA = Equivalent sound absorption area (A = a · S)a = frequency-dependent (6 octaves)S = actually occupied areaMusicSpeechTeachingSport 1Sport 2dB40302010807060501009060TNt (sec)0125 250 500 1,000 2,000 4,0000.51.01.52.0TN (s)f (Hz)0.51.01.52.0TN (s)f (Hz)0.51.01.52.0TN (s)f (Hz)This reverberation time belongs in a concert hallThis reverberation time is often found in offices. It rumblesReverberation target for multi-person offices.Ttarget = (0.45 lg V + 0.07) sm³Ttarget = (0.37 lg V – 0.14) sm³Ttarget = (0.32 lg V – 0.17) sm³Ttarget = (1.27 lg V – 2.49) sm³Ttarget = (0.95 lg V – 1.74) sm³Acoustics defined Key concepts in room acoustics and sound insulationAreas of acousticsPage 2 Page 2 Page 3125 250 500 1,000 2,000 4,000 125 250 500 1,000 2,000 4,000Important technical standards and guide-linesSound absorbers for room acoustics and sound insulationOther important tech-nical terms Page 4 Page 7 Page 8Did you know that ...... the speed of sound in air depends not on pressure but on temperature? Sound travels faster with rising temperature.... the German word “Lärm” comes from “a l’arme”? The French expression is derived from the Italian “all’arme”, literally “to your weapons”.Sound pressure p and sound pressure level LP: The sound pressure is the amplitude of an oscillation. It is very small compared with atmospheric pressure at rest (approx. 100 kPa) (sound pressure p = 20 Pa = pain threshold). Logarithmic rules must be observed when calculating levels.Sound pressure level LP = 20 lg p/p0 dBThe total sound power is determined by adding the in-dividual powers together: [12/16]Acoustics defined Key concepts in room acoustics and sound insulationAreas of acousticsPage 2 Page 2 Page 3Sound absorption coefficient a : This means the ratio of the sound energy not reflected from a surface to the sound energy falling on the surface. With total sound reflection the sound absorption coefficient a = 0, with total sound absorption a =1. The absorption coefficient is determined in a reverberation room according to DIN EN ISO 354 (Measurement of sound absorption in reverberation rooms, December 2003 edition). The fre-quency distribution of acoustic events is also impor-tant for planning. The sound absorption coefficient of materials and objects is used to determine this. Rated sound absorption coefficient a W : Single value indicating the sound absorption capacity of a material. It is obtained by comparing the practical sound ab-sorption coefficients a P with the values of a reference curve according to DIN EN ISO 11654.Practical sound absorption coefficient a P : Sound absorption coefficient for octave band, calculated ac-cording to DIN EN ISO 11654.The sound absorption coefficienta (dimensionless) indicates how much of the sound energy hitting a surface is absorbed: 0.0 –1.0 = 0–100%Frequency (Hz) 125 250 500 1,000 2,000 4,0001.21.00.80.60.40.20Product example ap 0.10 0.25 0.65 0.95 1.00 1.00ap63 125 250 500 1,000 2,000 4,000 8,000–20–1001020Frequency f (Hz)Sound pressure level difference LP –L P1000 (dB)–30Male voiceFemale voicenLtarget = 0.45 lg ? 10 Lj dBj = 110 3 2.5 2 1.5 0.5 00 1 2 3 6 8 15Surcharge on the higher levelL (dB)Difference between two levels L1 – L2 (dB)7 9 10 2014 5[13/16]Important technical standards and guide-linesSound absorbers for room acoustics and sound insulationOther important tech-nical terms Page 4 Page 7 Page 8Acoustics PrimerSound pressure level LP for sound propagation in the open air: The relationship between sound pressure lev-el LP on an enveloping surface S and sound power level LW of the source is given by the following equation:LP = LW –10 lgS dBFor an enveloping surface of 1 m², sound pressure level and sound power level are numerically equal. For spherically radiating sources, at a distance s from the center of the source:LP = LW –11–20 lgs dBFor hemispherically radiating sources, where the sound power is distributed over an enveloping surface that is only half as large, the sound pressure level at the same distance s is 3 dB higher:LP = LW – 8–20 lgs dBLongitudinal acoustic attenuation R: This term refers to the acoustic quality of a building component parallel to its propagation direction. RW is the quality of a component perpendicular to its propagation direction. The values RW or RL,W of a build-ing component may be of interest depending on the direction of view.RW = D + 10 lg (S/A)D = measured sound level differenceS = area of the building component to be isolatedA = equivalent sound absorption areaThe measured sound level difference D can vary for the same component but with a different surface area or room arrangement. Therefore RW is not determined solely by measurement, but is always measured and calculated. Only the level difference D can be deter-mined by measurement alone.Resulting sound attenuation RW, res : For a building com-ponent consisting of n sub-areas, the resulting sound attenuation RW, res is obtained from the sound attenua-tions Ri of the individual sub-areas:For two sub-areas S1 and S2 with sound attenuations R1 and R2 the equation can be simplified as follows:Speech communication: Transmission or exchange of information for achieving communication between people. This is done not only using the spoken word, but also through facial expression, gestures and body language.RWRL, WRL, WRL, W RL, WRres = – 10 lg { 1 (S1 · 10 – R1 / 10 + S2 · 10 – R 2 / 10) } dBS1 + S2Rres = – 10 lg dB? Si · 10 – R i / 10j = 1n? Si j = 1n[14/16]Acoustics defined Key concepts in room acoustics and sound insulationAreas of acousticsPage 2 Page 2 Page 3Speech sound pressure level LSA: Equivalent, A-rated sound pressure level of speech, measured at the ear of the listener. The value of the speech sound pres-sure level, measured at a distance of 1 meter from the speaker, is given as LPA, 1 m and characterizes the speaker’s way of speaking.Speech intelligibility: Basic criterion of acoustic qual-ity in speech performance rooms. The subjective in-telligibility of speech may be determined based on the percentage of correctly recognized syllables, words or sentences. Objective measurement methods allow us to determine the intelligibility of speech from the physical parameters of speech communication in the room – speech level, sound propagation, background noise etc.Background noise level: This refers to a sound pres-sure level containing various extraneous noises which can be heard by the user.Total background noise level LNA : Sound pressure level containing all noise components reaching the listener during the period of use. This includes building noises, operating noises and public noises. The A-rated total background noise level LNA is usually determined at ear height and stated in decibels.Background noise level of building noises LNA,Building : Sound pressure level in the observed room which is generated by noises from neighboring rooms, building service installations, sanitary installations and perma-nently installed audiovisual equipment. The A-rated background noise level LNA,building is stated in decibels.Background noise level of operating noises LNA,operating: Sound pressure level of additional equipment being operated in the room, such as mobile playback sys-tems for images and sound etc.Wavelength ? : The wavelength is the distance be-tween two successive points in a propagating wave where the oscillation state is identical – for example between two peaks:? = c / f = c · Tc = speed of sound (approx. 343 m/s at 20°C) f = frequency in HzT = time5 2 1 0.5 0.2 0.163 125 250 500 1,000 2,000 4,000Wavelength ?0 (m)Frequency f (Hz)Important technical standards and guide-linesSound absorbers for room acoustics and sound insulationOther important tech-nical terms Page 4 Page 7 Page 8Did you know that ...… for effective hearing protection at noise levels above 120–125 decibels, you need to wear a sound-proof suit? This is because the inner ear also registers sound waves sensed through the body. Therefore under conditions of extremely high noise, the whole body needs to be protected from the environment. [15/16]Acoustics PrimerKey termsTerm Symbol Unit PageRoom noise 3Free-field noise 3Sound absorption and reflection 4Sound pressure level LP dB 4,12Standards and guidelines 4,6,7Absorber classes 7Equivalent sound absorption area A m2 8Frequency f Hz 8Acoustic quality 10Reverberation time T sec 10Sound absorption coefficient a 12Rated sound absorption coefficient aW 12Practical sound absorption coefficient aP 12Sound pressure P Pa 12Longitudinal acoustic attenuation RW dB 12Resulting sound attenuation RW,res dB 13Speech communication 13Speech sound pressure level LSA dB 13Speech intelligibility 14Background noise level dB 14Total background noise level LNA dB 14Background noise level of building noises LNA,Building dB 14Background noise level of operating noises LNA,operating dB 14Wavelength ? m/sec 14Status of manufacturer information: 06/07. Subject to technical changes. pinta acoustic gmbhOtto-Hahn-Straße 782216 Maisach, Germanyphone +49 (0)8141. 88 88-0 fax +49 (0)8141. 88 88-555info@pinta-acoustic.dewww.pinta-acoustic.de