Chapter 2. Physiological acoustics, decibel. The decibel (1/2) Sound levels (2/2) Sound levels (1/2) The decibel. Equal loudness contours

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1 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 Chapte Physiological acoustics, decibel The sensitivity of human ea depends on the fequency The auditive sense is popotional to the logaithm of the acoustical intensity I of the wave L = 1 log ( I ) 1 I s s The decibel (1/) 1 with I = 1 W. m db I N F R A S O U N D S Theshold of audibility Theshold of pain Audible aea Speech 1 Hz Hz 1 khz khz khz The unit fo the sound level is the decibel (db) (one tenth of a bel), named like this in honou of the physicist Alexande Gaham Bell. This unit has the advantage of being based vey well on the diffeential sensitivity of human ea, since 1 db gap between two sound levels substantially coesponds to the smallest diffeence (in sound level) detectable by the human ea. U L T R A S O U N D S fequency Alexande Gaham Bell ( , ameican invento) The sensitivity of human ea depends on the fequency The auditive sense is popotional to the logaithm of the acoustical intensity I of the wave L = 1 log ( I ) 1 I s I p ms s Sound levels (1/) 1 with I = 1 L = log W. m db ( p ) 1 m s p s I N F R A S O U N D S Theshold of audibility 1 Hz Hz 1 khz khz khz p s = ρ c I s = Theshold of pain Audible aea Speech U L T R A S O U N D S fequency = 1 Pa 3.5 L es -L 1 (db) Sound levels (/) Sound level which esults fom two non-coelated souces L 1 1 L 1 ( 1 1 ) I 1 + I L es = 1 log 1 = 1 log 1 + I s P tot p aveages p () ove time, ove an acoustic = v () = ρ () peiod T: = 1.5 P E T p ms = () [ p( ; t) ] with 1 T + T [ p( ; t) ] = lim [ p( ; t) ] T T d t 1.5 L -L 1 (db) time (s) [ p( ; t) ] [ p( ; t) ] es ( L es L 1) L 1 L = + with L es ( L L 1) 1 L 1 = 1 log 1 ( 1+ 1 ) Acoustic pessue µpa jet engine (distance: 5 m) pop band libay 1 1 tuck bedoom speech 1 1 buit noise Acoustic pessue level db 14 theshold of pain living oom 3 1 The decibel take-off (distance: m) pneumatic dill oad taffic mountain office theshold of audibility Pa,,,,, db = X 4 db and 4 db = 43 db + = 4 db and 14 db = 14 db Equal loudness contous pessue level Lp (db) theshold of audibility theshold of pain fequency (Hz) loudness: subjective intensity of a sound; unit: thephon Example: A 7 phons sound povokes the same auditive peception than a Hz sound, the physical level of which is 7 db 1

2 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 A weighting cuves: db(a) high pitch and low pitch sounds ae less peceived tempoal lobe of bain Stuctue of human ea semi-cicula malleus incus canals oval window auditoy neve cochlea pinna tempoal bone auditoy canal eadum stapes cicula window eustachian tube Oute ea Middle ea Inne ea Ossicles The tympanic membane (eadum) incus malleus stapes Fom Robie Tansfe of acoustic pessues (sonic waves) fom ai medium to fluid media and to inne ea stuctues (cochlea) incus malleus "small" displacement (not vey compessible liquid) stength "highe" and S smalle ==> highe pessue stapes stapes pivot ossicles eadum Tansfe of acoustic pessues (sonic waves) fom ai medium to fluid media and to inne ea stuctues (cochlea) - animation The sound wave moves the eadum and attached ossicula chain. The stapes footplate, in the oval window, tansfes the vibations to the peilymphatic compatment (scala vestibuli) and to the inne ea stuctues. Depending on the fequency, the vibation has a maximum effect (esonance) at a diffeent point along the basila membane, accounting fo passive tonotopy. eadum "lage" displacement (compessible gas) "less lage" stength and geate S ==> smalle pessue a high fequency sound affects a basal potion of the cochlea a low fequency sound affects a moe apical pat of the cochlea Text and images fom website "Pomenade 'ound the cochlea" ( by R Pujol et al., Univesité Montpellie 1 et INSERM - Fance

3 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 Schematic functioning of the eadum Cochlea - Ogan of Coti - Hai cells scala vestibuli ea eadum scala tympani cochlea tunnel ogan of Coti oute hai cells inne hai cells nose equilibium of pessues healthy cells damaged cells neve fibes of the auditoy neve Hai cells Audiogams Heaing fequency (Hz) Heaing loss (db) nomal heaing heaing loss eaches Hz heaing loss at 4 Hz impotant o ievesible deafness Too much silence? Sound levels - Noise annoyance Dange at wok (weaing of had hat) in the steets (noiseless vehicles) Depivation of sound infomation noise of an engine functioning of a machine lack of pleasantness (the good noise!) The audible sounds ange fom db (theshold of heaing) and 14 db. The theshold of pain is aound 1 db. Annoyance, which is a subjective concept, is felt with a geat vaiability fom one peson to anothe. Consequently, no objective noise level can give an absolute indication of the annoyance. Discomfot public tanspots (tain) open-plan offices 3

4 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 Teestian tanspots Noise contou maps (Pais - Fance) Exposue of population to oadway noise: numbe of oad black points Nod Pas-de-Calais Leq 7 db(a) between 8 h - h Haute Nomandie Picadie Loaine Basse Nomandie Ile de-fance Betagne Champagne Adenne Alsace Pays-de-Loie Cente Bougogne Fanche Comté Poitou Chaentes Aquitaine Limousin Auvegne Rhône-Alpes Povence Fom data bank of LRPC Stasboug - Fance (esults 1998) Alpes Côte d'azu 1st distict Midi-Pyénées Languedoc Roussillon 16th distict Fench noise annoying plan (plan de gène sonoe - PGS in fench) Fench noise annoying plan (plan de gène sonoe - PGS in fench) Document povided by Fench law of 31 Decembe 199 (Aticle 19) which pemits to define the aeas in which esidents ae eligible fo assistance fo soundpoofing. Roissy CDG Aipot (1999) Fench noise exposue plan (plan d'exposition au buit - PEB in fench) Fench noise exposue plan (plan d'exposition au buit - PEB in fench) Document povided by the Fench law of 11th July 1985 which egulates ubanism nea aipots so as not to expose new populations to noise annoyance. Specific measues can take into account the specificities of the pe-existing context. Oly Oly- Fance Oly aipot Pecautionay pinciple 4

5 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 PEB - PGS: mege? An fench inteministeial woking goup studied the question of binging togethe the pocedues elating to the noise exposue and noise annoying plans in Fance. A epot eleased in Decembe 7 weighs the advantages and disavantages of a mege of the two zonings, and makes poposals. Example of solution: taffic management (noise mitigation) Maximum numbe aicafts movements (Oly aipot :. pe yea) Time of day estictions (Oly aipot : 7 am to 11 pm) Choice of ai lanes Depatue flight path and slope Repot of the woking goup «Rappochement des pocédues PEB et PGS» - epot n june 7 (fomat pdf - 784,9 Ko) - Authos : Gilles Rouques (CGPC) and Annick Helias (IGE) B_et_PGS.pdf o Sounds Peception and oom acoustics (1/1) Peception Peception and oom acoustics (/1) noise (annoyance, alet function) speech (intelligibility) music (esthetic) spectum intensity duation oganization of sounds time (ythm, melody) spatial (fill the space) space - visually - auditively peceived Location: compaison by the bain of intensities times of aival Attibutes: monaual heaing binaual heaing Continuous: fomants fo the voice Tansient: consonants, musical attack to the two eas loundness, pitch, timbe (timbe), soundscape d B ms L d B tms Peception and oom acoustics (3/1) The sound space Location of one souce binaual pinna scatteing d B ms Location of two souces coheent souces: impossible non coheent souces: distinct L d B tms Peception and oom acoustics (4/1) Soundscape: intelligibility and noise Noise masking speech Example: penicious effect of evebeation Revebeation which pemits to the speake to hea himself Too high evebeation: tiedness h(t) Delay between two coheent souces summation effect (~ 1ms) pecedence effect (loudness + space effect) space effect (3D) These thee effects can be simultaneously peceived (eflections in a oom) Lage numbe of eflections, late effects: evebeation ms staightfowad sound 1st (geometical) eflections evebeation (statistics) time 5

6 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 Peception and oom acoustics (5/1) Soundscape, oom acoustics (1/6) Expectation of the listene Expectation of the pefome blooming, esthetic pleasue intepetation of music The listene ty to: benefit fom a sonoous sound (avoid tiedness) make the most of his two eas (space effect) well undestand music (but small "fuzziness") have a good adjustment of tones (instumental equilibium, tonal equilibium, ) Moeove, the musician ty to: well listen what he is playing have a good contact with othe musicians Peception and oom acoustics (7/1) Soundscape, oom acoustics (3/6) Musicians listen what they ae playing etun of sound towads stage good coupling stage / oom Peception and oom acoustics (6/1) Soundscape, oom acoustics (/6) Listenes Sonoous sound Ochesta: 1 to W (in facts < 11 db) good distibution of sound enegy incease the numbe of eflections incease the volume of the oom (6 to 11 m 3 pe listene) Use of the two eas initial side eflections (close to the listene) impove the claity Good undestanding limited evebeation (compomise with sonoousness) favo the small "fuzziness" Good adjustement of tones (delicate) avoid font eflectos (above and behind the ochesta), coloation if the eflecto ae pesent, split them Peception and oom acoustics (8/1) Soundscape, oom acoustics (4/6) Impulse esponse () t h () t *p () t p = anechoic good contact between them eflectos above the ochesta The oom Room acoustics question of geomety aangement of volumes aangement of walls contact listenes / musicians coupling stage / oom Absobant acoustical teatment does not impove anything (pemits eventually to emove some echoes) h(t) ms staightfowad sound 1st (geometical) eflections evebeation (statistics) time Peception and oom acoustics (9/1) Soundscape, oom acoustics (5/6) Subjective chaacteization Revebeation Claity Loudness Intimacy Unifomity Diffusion Envelopment Pefome's satisfaction Questionnaie Binaual heaing numeical simulation, scale model Peception and oom acoustics (1/1) Soundscape, oom acoustics (6/6) Objective chaacteization (examples) sound amplitude evebeation duation at -6 db ealy decay time (1st eflections) 8 ms 1 log1 p () t d t p () t d t 8 timbe 5 Hz 5 Hz 1 log1 M() f d f 45 M() f d f 5 Hz 5 Hz Numeical simulation Scale model 1 log p () t 1 d t p ef 45 6

7 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 lage movie pojection sceen on a pefectly eflecting wall Example of mistakes (1/) McKinnon Theate, Ketteing Univesity, Flint, MI flutte echo Example of mistakes (/) succesive echoes lage movie pojection sceen on a pefectly eflecting wall 4 seats McKinnon Theate, Ketteing Univesity, Flint, MI Animation coutesy of D. Dan Russell, Ketteing Univesity 7

8 C. Potel, M. Buneau, "Acoustique généale (...)", Ed. Ellipse, collection Technosup, ISBN , 6 Slides based upon C. POTEL, M. BRUNEAU, Acoustique Généale - équations difféentielles et intégales, solutions en milieux fluide et solide, applications, Ed. Ellipse collection Technosup, 35 pages, ISBN , 6 8