Presentation on theme: "AN INTRODUCTION TO SOUND AND NOISE J. Fogola, D. Grasso Regional Agency for the Protection of the Environment of Piedmont (Arpa Piemonte) Comenius Project."— Presentation transcript:
AN INTRODUCTION TO SOUND AND NOISE J. Fogola, D. Grasso Regional Agency for the Protection of the Environment of Piedmont (Arpa Piemonte) Comenius Project Torino, October 4° 2012
Everyday our world is filled with a multitude of sounds Sound can let us communicate with others or let others communicate with us It can be a warning of danger or simply an enjoyable experiencewarning of danger enjoyable experience INTRO
WHAT IS SOUND? Sound is produced when something vibrates….
….and generates a sequence of waves of pressure that propagates through compressible media WHAT IS SOUND?
ACOUSTICS Term derived form Ancient Greek akoustikòs (akoùo, “I hear”) It’s the branch of physics that deals with the study of the sound SOURCE RECEIVER PROPAGATION
Different physical phenomenon SOURCES Mechanical (bell ringing, explosions,…) Fluid dynamics (sound from fan,…) Electromagnetic ( magnetostriction in the core of a transformer ) Thermic (boiler combustion,…)
Sound can propagate through solid, liquid or gas PROPAGATION BUT WHAT IS PROPAGATING? Just energy!
Temperature [°C] Speed of sound [m/s] Speed of sound changes with temperature PROPAGATION
Medium Steel Aluminum Concrete Rubber Marble Wood Lead Glass Speed of sound [m/s] ….and it changes with medium Density [kg/m 3 ] PROPAGATION
Not only human being, but any living form (ecosystem) RECEIVER
ACOUSTICS IS MULTIDISCIPLINARY The combination of different sources, means of propagation and receivers makes the acoustics a multidisciplinary science
ACOUSTICSAPPLICATIONS MILITARY APPLICATIONS ARCHITECTURE ( theaters, concert halls, buildings,..) DIAGNOSTICS (medicine, structural) TELECOMMUNICATION ENGINEERING (automotive, industry….) ELECTROACUSTIC (loudspeakers, elect. devices,…) ENVIROMENT MUSIC JUSTICE (phone tapping, identification of the speaker,… HEALTH IN WORKING PLACE
PROPRIETIES OF SOUND Intensity or Volume (dB) - proportional to the energy of the sound - expressed in a logaritmic scale (dB) - defined ad Sound Pressure Level or SPL Getting closer Far from the source
FREQUENCY Frequency refers to the number of vibrations that an individual particle of the mean of propagation makes in a a second It’s measured in hertz (Hz)
FREQUENCY Each natural or anthropic sound can be decomposed in all the frequencies of the range of human hearing (20 – Hz), such as the natural light can be decomposed in all the visible colors of the rainbow
Sound pressure level vs Frequency
The sensitivity of the ear changes for the different frequencies A5 (880 Hz) A2 (110 Hz) To take into account of the response of the ear, the dB(A) is introduced dBdB (A) SPL is weighed in frequency with the so called “A” curve
….but dB(A) is not enough!
physics psychoacoustics psychology Sound Event Hearing Event The human hearing: from a sound event to a hearing event
Sound Content Classification of Sound Event Level, lin., A-, B-, C-weighted Duration Time Energy Spectral Contribution Temporal Structure Quantity Position Spatial Distribution Subjective Attitude Signal Information Physical AspectPsychoacoustical AspectBinaural AspectCognitive Aspect
Etymologically, the word “noise” can be traced back to the high French period term noyse and to the eleventh century provencal terms, noysa, nosa, nausa, but its origin is still uncertain. The term has a variety of meanings and nuances, the most important are the following: Unwanted sound SOUND OR NOISE? Not musical sound High intensity sound Disturbance within any communication system
NOISE = unwanted sound SUBJECTIVE PleaseUnpleaseSound SOUND OR NOISE?
….it depends from specific culture
The society can fix wanted and unwanted sounds, in relationship to the consensus of the people The language can show the attitude of a nation to consider a sound as noise or not (in France the term bruit in used both for the emission of a jet and for the rastle of birds) NOISE = unwanted sound SUBJECTIVE ….it depends from specific culture
CONTEX is IMPORTANT At PM in a concert hall At PM in the bed trying to sleep with the neighbors that listen to music In the middle of a busy area In the middle of a park
Working and leisure activities can produce hearing loss AUDITORY EFFECTS
HEARING LOSS IS NOT DEPENDENT ON THE PLEASURE OF LISTENING
An exposure to 105 dB(A) for 5 years and 4 hours per week, tipical in disco, is comparable to an exposure to 85 dB(A) for 30 years and 40 hours per week, maximum tolerable exposure in a working place for Italian regulation AUDITORY EFFECTS …from a scientific study…
Normal hearing Hearing loss AUDITORY EFFECTS
SOLUTIONS In the working places Prevention and protection
For other activities Keeping low the volume in the headphones Limiting exposition in disco and pub
Produced by environmental noise NON-AUDITORY EFFECTS
Influence on sleep (the example of air traffic noise) Change of stage (EEG) Mean motilityMotility after single eventUnconscious awakening (EEG) Conscious awakening NON-AUDITORY EFFECTS
Self reported sleep disturbance
NON-AUDITORY EFFECTS Reduction of cognitive performance A reduction of exposure levels of 5 dB(A), in the range between 65 and 80 dB(A), increases the cognitive performance up to 10% and the attention and the memory up to 2-3%
Cardiovascoular Biological Mental health NON-AUDITORY EFFECTS Long term effects