DENORMS TRAINING SCHOOL 3 “Experimental techniques for acoustic porous materials and metamaterials” 4 – 6 December 2017, Le Mans Introduction to psychoacoustics and psychoacoustic tests Assoc. Prof. Kristian Jambrošić, PhD [email protected] University of Zagreb, Croatia Faculty of Electrical Engineering and Computing Motivation Physics is just something we measure. Reality is what we perceive. Jens Blauert 2 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Contents . Overview of the hearing process . Sound reproduction systems . Acoustic comfort . Psychoacoustics and psychoacoustic parameters . Listening tests . Examples (case studies) 3 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests . Overview of the hearing process . Sound reproduction systems . Acoustic comfort . Psychoacoustics and psychoacoustic parameters . Listening tests . Examples (case studies) 4 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Anatomy of the ear . Our sense of hearing = ear + auditory center in the brain . Parts of the ear: . outer ear . middle ear . inner ear hearing process 5 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Hearing process . Basics of the hearing process: . Sound waves enter the ear through the pinna and the ear canal which causes the eardrum to move. The eardrum vibrates with sound, very similar to a membrane of a microphone. Sound vibrations move through the ossicles to the cochlea like a system of leavers. Sound vibrations cause the fluid in the cochlea to move forth and back (movements equalized by the round window). Fluid movement causes the hair cells to bend. Hair cells create neural signals which are picked up by the auditory nerve. Hair cells at one end of the cochlea send low pitch sound information and hair cells at the other end send high pitch sound information. The auditory nerve sends signals to the brain where they are interpreted as sounds. 6 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Middle ear . Middle ear is responsible for sound conduction, but also for the acoustic reflex (protective mechanism) 7 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Inner ear 8 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Organ of Corti 9 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Frequency selectivity of the Cochlea © Fastl, Zwicker: “Psychoacoustics” 10 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Neural response of the auditory nerve . The amplitude (intensity) of the perceived sound wave is coded in auditory nerve firing impulses . Higher amplitude is coded with higher firing rate! 11 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests © Gelfand: “Hearing” Hearing threshold . Average hearing threshold of human 12 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Hearing threshold . What is the lowest sound pressure we COULD hear? . Brown noise – movement of the air molecules , constant noise at about -20 to -30 dB at mid freuqencies! 13 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Hearing threshold . Hearing threshold for other marine and land mammals: 14 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Hearing threshold . Highest audible frequency versus interaural distance: © http://acousticstoday.org/wp-content/uploads/2016/01/The- 15 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Evolution-of-Mammalian-Sound-Localization.pdf Hearing threshold . Hearing vs. vision for some mammals © http://acousticstoday.org/wp-content/uploads/2016/01/The- 16 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Evolution-of-Mammalian-Sound-Localization.pdf Auditory masking . The masking effect by a masking tone and the new masking threshold: 17 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Auditory masking . New hearing threshold because of masking tone: . Temporal masking: © Fastl, Zwicker: “Psychoacoustics” © Fastl, Zwicker: “Psychoacoustics” 18 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Binaural hearing (using 2 ears) enables directional hearing – localization of sound sources in a 3D space with a certain precision © Blauert: “Communication Acoustics” 19 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Sound localization requires some mechanisms: . interaural time difference (ITD) – mechanism that functions up to 2000 Hz . interaural level difference (ILD) – mechanism that functions from 500 Hz . dynamic localization by head movement – improves the precision of sound source localization . head related transfer functions (HRTF) – mechanism that enables sound localization in the median plane . auditory scene analysis – includes higher brain functions for sound source recognition and analysis 20 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Interaural time and level difference overview 21 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . ITD can go up to 0,6 ms for the average person . ILD depend on the difference level (because of the JND – Just Noticeable Difference) © Psychology course; http://www.appstate.edu/~steelekm/classes/psy3203/topics_F05.htm 22 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Localization precision as function of sound source azimuth and its frequency 23 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Cone of confusion – places with same ITD and ILD . Solution – dynamic localization by head movement (functions for signals longer then 1 s) © http://gyronymo.free.fr/audio3D/the_experimenter_corner.html 24 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Since the head is not round, and the torso also reflects sound . The sound signal recorded at the left and right ear will be significantly different even on the cone of confusion (HRTF!) . This effect is highly frequency dependent 25 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests © http://gyronymo.free.fr/audio3D/the_experimenter_corner.html Binaural hearing . HRTF – the reason why we are able to localize sounds in the median plane 26 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Measurements of individual HRTF’s 27 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . HRTF differences for 2 persons, same direction 28 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . HRTF difference for same person (3 measurements), different directions . Localization is better for broadband sound . This is especially true above 6 kHz where HRTF’s have greatest differences 29 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . HRTF’s and learned (from own listening experience) . If a narrowband noise signal is played anywhere from the medial plane, the sound direction seems to change with the change of the source frequency . Several seconds of learning process 30 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Auditory scene analysis 31 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . auditory scene analysis 32 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Auditory system computer models - signal driven process (bottom-up) © J. Blauert, Communication Acoustics 33 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Binaural hearing . Experiment for 2 simultaneous speech source in a real room 34 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Hearing and space © http://gyronymo.free.fr/audio3D/the_experimenter_corner.html 35 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Precedence effect . Primary effect for understanding the creation of phantom sources; the other is amplitude panning sine signal L 50ms L 5ms L 1ms C R 1ms R 5ms R 50ms 36 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Amplitude panning . The phantom image is moved by different intensities emitted by 2 or more coherent sound sources sin g g i 1 2 sin0 g1 g2 37 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Amplitude panning . Why the perceived source is called “phantom source”? 38 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Trade-off (Haas effect) . Interaction between interaural time & intensity differences 39 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Spaciousness . The influence of only one direct + one reflected sound wave 40 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Franssen effect . But… 41 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests . Overview of the hearing process . Sound reproduction systems . Acoustic comfort . Psychoacoustics and psychoacoustic parameters . Listening tests . Examples (case studies) 42 DENORMS TRAINING SCHOOL - Psychoacoustics and psychoacoustic tests Principles of psychoacoustics . Psychoacoustics - science of sound perception . It investigates statistical relationships between acoustic stimuli and hearing sensations . Psychoacoustic models mimic the hearing mechanism . A good understanding of the sensory response of the human auditory system (HAS)