Introduction to psychoacoustics and psychoacoustic tests

Transcription

1 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 kristian.jambrosic@fer.hr University of Zagreb, Croatia Faculty of Electrical Engineering and Computing

2 Motivation Physics is just something we measure. Reality is what we perceive. Jens Blauert 2

3 Contents Overview of the hearing process Sound reproduction systems Acoustic comfort Psychoacoustics and psychoacoustic parameters Listening tests Examples (case studies) 3

4 Overview of the hearing process Sound reproduction systems Acoustic comfort Psychoacoustics and psychoacoustic parameters Listening tests Examples (case studies) 4

5 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

6 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

7 Middle ear Middle ear is responsible for sound conduction, but also for the acoustic reflex (protective mechanism) 7

8 Inner ear 8

9 Organ of Corti 9

10 Frequency selectivity of the Cochlea Fastl, Zwicker: Psychoacoustics 10

11 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 Gelfand: Hearing

12 Hearing threshold Average hearing threshold of human 12

13 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

14 Hearing threshold Hearing threshold for other marine and land mammals: 14

15 Hearing threshold Highest audible frequency versus interaural distance: 15 Evolution-of-Mammalian-Sound-Localization.pdf

16 Hearing threshold Hearing vs. vision for some mammals 16 Evolution-of-Mammalian-Sound-Localization.pdf

17 Auditory masking The masking effect by a masking tone and the new masking threshold: 17

18 Auditory masking New hearing threshold because of masking tone: Temporal masking: Fastl, Zwicker: Psychoacoustics 18 Fastl, Zwicker: Psychoacoustics

19 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

20 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

21 Binaural hearing Interaural time and level difference overview 21

22 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; 22

23 Binaural hearing Localization precision as function of sound source azimuth and its frequency 23

24 Binaural hearing Cone of confusion places with same ITD and ILD Solution dynamic localization by head movement (functions for signals longer then 1 s) 24

25 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

26 Binaural hearing HRTF the reason why we are able to localize sounds in the median plane 26

27 Binaural hearing Measurements of individual HRTF s 27

28 Binaural hearing HRTF differences for 2 persons, same direction 28

29 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

30 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

31 Binaural hearing Auditory scene analysis 31

32 Binaural hearing auditory scene analysis 32

33 Binaural hearing Auditory system computer models - signal driven process (bottom-up) 33 J. Blauert, Communication Acoustics

34 Binaural hearing Experiment for 2 simultaneous speech source in a real room 34

35 Hearing and space 35

36 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

37 Amplitude panning The phantom image is moved by different intensities emitted by 2 or more coherent sound sources sin sin i 0 g g 1 1 g g

38 Amplitude panning Why the perceived source is called phantom source? 38

39 Trade-off (Haas effect) Interaction between interaural time & intensity differences 39

40 Spaciousness The influence of only one direct + one reflected sound wave 40

41 Franssen effect But 41

42 Overview of the hearing process Sound reproduction systems Acoustic comfort Psychoacoustics and psychoacoustic parameters Listening tests Examples (case studies) 42

43 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) is essential to the development of psychoacoustic models where the perceptual quality of processed audio must be preserved to the greatest extent. (Y. Lin, W. H. Abdulla. Audio Waterk, Ch. 2 - Principles of Psychoacoustics, Springer 2015) 43

44 Auditory tests and psychoac. measurements Sound stimuli often used in psychoacoustic tests 44 Fastl, Zwicker: Psychoacoustics, pp. 2

45 Loudness Loudness = intensity sensation besides loudness of singular sound events, the loudness of partially masked sounds is often perceived as well (referent sound + masking sound simultaneously) JND (just noticeable difference) of loudness is around 1 db Fastl, Zwicker: Psychoacoustics, pp

46 Loudness Loudness level in phones = 1 khz Gelfand, Hearing, pp. 208

47 Loudness Phone curves 47 Brüel & Kjaer, Fundamental of measuring Sound, 2007

48 Loudness A-weighting filter (A-level, dba) 48

49 Loudness 0 db HL 49 0 phone

50 Loudness Hearing loss categories 50

51 Loudness Cochlear implant for patients that still have the auditory nerve working 51

52 Loudness Typical loss of hearing sensitivity with age Fastl, Zwicker: Psychoacoustics, pp

53 Loudness Relation between SPL increase and hearing sensation 53

54 Loudness Sone is a unit of loudness that relates to how loud a sound is perceived Sone scale is linear Doubling the perceived loudness doubles the sone value! Loudness of 40 phon (L N ) equals loudness of 1 sone (N), for loudness above 40 phon or 1 sone! Gelfand, Hearing, pp

55 Loudness Example of loudness calculation procedure using a charts indicating measured third-octave band levels of a factory noise Loudness war! Fastl, Zwicker: Psychoacoustics, pp

56 Pitch Pitch = frequency sensation Double pitch is perceived as an octave (double or half frequency of a referent sound), but not above 1 khz 50 Hz -> jnd = 3 Hz 150Hz -> jnd = 2 Hz 1000 Hz -> jnd = 4 Hz 3000 Hz -> jnd = 18 Hz Hz -> jnd = 90 Hz 56

57 Pitch The pitch of a complex tone doesn t change with taking away the fundamental of the tone It is only perceived as a change in timbre (orchestras with different instruments) Pitch perception depends on frequency, duration, intensity 57 Gelfand, Hearing, pp. 225

58 Pitch Different instruments have different levels of harmonics, but they still retain the same pitch A good example here 58

59 Sharpness Sharpness is linked to the spectral characteristics of the sound A high-frequency signal has a high value of sharpness (thus, sharpness is usually inverse to sensory pleasantness) This metric is measured in acum Sharpness of one acum is produced by a band of noise onecritical band wide centered on 1 khz having a level of 60 db 59

60 Sharpness The value of g(z) is unity for critical band rate from 0 to 16 Bark, and rises to a value of 4.0 by the time 24 Bark is reached 60

61 Sharpness Sharpness is linked to the spectral characteristics of the sound Sharpness can be a useful measure where the high frequency content of a sound is important to a product's quality 61

62 Roughness It describes the human perception of temporal variations of sounds This metric is measured in asper One asper is defined as the roughness produced by a 1000Hz tone of 60dB which is 100% amplitude modulated at 70Hz 62

63 Roughness If a tone (e.g. 1 khz sine) is 100% amplitude modulated, our sensation depend on the modulation frequency The first sensation experienced is fluctuation strength, where the individual loudness modulations are audible This experience peaks at 4 Hz Once the modulation frequency reaches 15 Hz, the sensation of roughness begins to appear rough sounds not rough sounds 63

64 Fluctuation strength Fluctuation strength is similar to roughness except it quantifies subjective perception of slower (up to 20Hz) amplitude modulation of a sound Generally, fluctuation strength is perceived as an irritating property (alarm sounds!) Fluctuation strength of one vacil is defined by a 60 db 1 khz tone 100% amplitude modulated at 4 Hz fluctuating sounds not fluctuating sounds 64

65 Combined psychoacoustics quantities Many times, different combined psychoacoustic quantities are needed to set a formula for expressing: sound quality of a certain product noise quality and noise annoyance soundscape quality, expectancy, acceptability Often, the percentile of loudness is another useful metrics, such as N 5, N 50, N 95 (for example N 5 is loudness value just exceeded for 5% of the measurement period) 65

66 Overview of the hearing process Sound reproduction systems Acoustic comfort Psychoacoustics and psychoacoustic parameters Listening tests Examples (case studies) 66

67 Psychoacoustic tests Sound quality is a descriptor of the adequacy of the sound attached to a product (Jens Blauert) 67

68 Psychoacoustic tests Psychophysics science of measuring human perception Steven s power law is a general relation between the physical strength of a stimulus and the subjective perception of that stimulus (valid for all senses) Psychophysical function: L = k I e L = perceived intensity k = person dependent constant I = physical intensity e = constant, depending on the sense 68

69 Psychoacoustic tests Weber s law statement about the JND (just noticeable difference) of the perceived quantity I = k I I = smallest detectable change in perception (just noticable difference JND) k = constant I = physical intensity 69

70 Psychoacoustic tests Finding a threshold in the threshold test (50%, 75%): 70

71 Psychoacoustic tests First, we made a statement, a hypothesis that gives information on the design of the experiment. There are 2 hypothesis types: Research hypothesis - verbal expression of the experimental test Statistical hypothesis - restatement of the research hypothesis to allow hypothesis testing In a research hypothesis (e.g. higher noise barrier decreases the perceived noise loudness at the imission point), there are 2 types of variables: Independent variable (barrier height, objectively measurable) Dependent variable (subjective rating of the sensation of noise level) 71

72 Psychoacoustic tests Statistical hypothesis (one or more) is an expression of the research hypothesis to allow testing First, the null hypothesis is formed (e.g., the barrier height has no effect on the perceived noise level) Then, the alternative hypothesis is formed (the independent variable has an effect on the dependent variable) Finally, the decision rule is formed in order to determine if the effect is due to chance Typically, p = 0.05 (1/20) chance of making an error is acceptable for rejecting the null hypothesis 72

73 Psychoacoustic tests Variables can be: 1. Quantitative interval or ratio parametric statistics can be applied data follows bell curve distributions, and center and width of the curve are of interest 2. Qualitative (nominal or ordinal) non-parametric statistical techniques are applied data represents number of scores within each category 73

74 Psychoacoustic tests Measurement types (according to T. Poulsen): 1. Threshold test To find out when a signal is just audible, just different from another etc. 2. Balance test To find out when a signal gives the same subjective experience as another signal (e.g. a reference signal). It could be in relation to loudness, pitch, duration, etc. 3. Scaling test The test signal is evaluated in relation to a scale, e.g., weakmedium-loud, the numbers from 1 to 10, etc. 4. Task test The test subject perform a given task in accordance with a given instruction. E.g. press a button when a certain situation occurs, repeat words transmitted through a transmission channel, solve calculation tasks, etc. 74

75 Psychoacoustic tests Measurement methods: 1. Classical psychometric methods Method of limits (descending, ascending, bracketing) Method of adjustment Method of constant stimuli 2. Method for eliminating subject bias: Classical solution - use of Catch trials (presentations without stimuli) Modern solution - criteria free procedures (unbiased), forcedchoice procedures, n-interval Forced Choice (n-ifc) or Alternative Forced Choice (AFC) methods 3. Adaptive methods: When trials do not give valuable information (if far away from the threshold which you are interested it). You have to have a qualified guess where the threshold is before using the methods. 75

76 Scales We need a metric (a measurement system) for evaluating sounds! Scales can generally fall into 4 categories: nominal scale, ordinal scale, interval scale and ratio scale Scales can be a good graphical aid. 1. Graphical (continuous) scales any value can be chosen from a continuous bar; there are only labels indicating the transition between 2 different descriptors 2. Categorical (discrete) scales the values are discrete, only discrete values can be chosen during the test (e.g. Likert scale with odd number of categories: 5, 7, 9, 11 ) Question: Do scales with the equidistantly distributed quality labels have perceptually equal-interval properties? This is a question of what a certain adjective means in a certain language (question of semantic differences)! 76

77 Differences in scaling and labels 77 Zielinski et al., 2007

78 Graphical scales in listening tests 78 Two type of graphical scales: 1. Continuous impairment scale typically for comparing evaluation of impairments exhibited my processed sound stimuli compared to unimpaired reference stimuli (recommended by ITU-R BS.1116 standard) 2. Continuous quality scale instead of impairment, labels of quality are given, and they do not define discrete points, but rather intervals (recommended by ITU-R BS.1534 standard) Zielinski et al., 2007

79 An example of using scales Zielinski et al.,

80 Overview of the hearing process Sound reproduction systems Acoustic comfort Psychoacoustics and psychoacoustic parameters Listening tests Examples (case studies) 80

81 Example 1 M. Horvat, K. Jambrošić, H. Domitrović, Influence of Short Term Noise on Concentration and Human Performance // NAG/DAGA 2009 International Conference on Acoustics, Influence of Short Term Noise on Concentration and Human Performance Four groups of test subjects were exposed to a specific type of noise: sinusoidal signal at 1 khz pink noise signal narrow band noise centered at 1 khz 1 khz sinusoidal carrier signal 100 % amplitude modulated with a 1 Hz sine The reference test was made in quiet for each group + in noise at 8, 16, 32 and 64 sone 81

82 Example 1 Some results: 82

83 Example 1 Humans can maintain concentration required for performing a given task when exposed to noise for a short period of time The increase of negative emotions like queasiness, tension and irritation is observed 83

84 Example 2 M. Horvat, H. Domitrović, K. Jambrošić, Sound Quality Evaluation of Hand- Held Power Tools. // Acta acustica united with acustica. 98 (2012), 3; Sound Quality Evaluation of Hand-Held Power Tools Power drills, hand-held circular saws and jigsaws have been chosen, recorded in idle working state and switch off phase Examples of category scaling and semantic differential used: Sound categories: loud, sharp, rough, stable, clean, trembling, muffled, crackling, rustling, clear, buzzing, harsh, howling and whistling Perception categories: unpleasant, beautiful, frightening, powerful, alarming, attractive, monotonous, repulsive and tense 84

85 Example 2 Jigsaw electric tool sounds Idling stage: Stopping stage: 85

86 Example 2 Ultimate goal of this and many other studies of sound quality: 86

87 Example 3 Sound Quality of Violins 87

88 Example Average sound quality score

89 Example 4 K. Jambrošić, M. Horvat, H. Domitrović, Assessment of urban soundscapes with the focus on an architectural installation with musical features. // The Journal of the Acoustical Society of America. 134 (2013), 1; Assessment of urban soundscapes with the focus on an architectural installation with musical features Urban soundscapes can be perceptually assessed by on-site surveys or laboratory tests and objectively evaluated based on monaural, binaural or multi channel recordings Sea organ Zadar Park in Zagreb Lendkai Graz Railways station Zagreb 89

90 Example 5 M. Horvat, K. Jambrošić, J. Francetić, H. Domitrović, M. Rychtarikova, V. Chmelik, On the Ability of Normal Sighted Persons to Assess Room Size and Position Inside the Room Based on its Acoustic Response. // Akustika. 24 (2015) ; 2-8 Self-localization - hand claps (own) of footsteps Room size assessment - central position - hand claps (own) 90

91 Example 5 Sound absorption α= 0.1 α= 0.2 α= 0.4 Scattering Walls + ceiling s= 0.05 Ceiling s= 0.9 One wall s= 0.9 Loudspeaker system Headphones 91

92 Example 5 Self localization Room size assessment Percentage of correct answers according to absorption - experiment 1 Percentage of correct answers according to absorption - experiment α 0.1 α 0.2 α α 0.1 α 0.2 α 0.4 clap - correct steps - correct clap - correct steps - correct 92

93 Rank Example 6 Klaus Genuit: Sound Design, Lecture at EAA Winter School, AIA-DAGA 2013, Merano Evader and similar projects search for best alarm sounds for electric and hybrid cars that are too quite Rank Pleasantness Rank Recognizability A B C D E F G H I J K L M N O P Q 93

94 Example 7 M. Horvat, J. Benklewski, K. Jambrošić, H. Müllner, M. Rychtarikova, R. Exel, The Challenges in Preparing the Stimuli to be Used in Subjective Evaluation of Impact Sound Insulation // Book of proceedings from ATF 2017, H2020 RISE Papabuild project 94

95 Example 7 How to compare the loudness of static and changeable sounds 95

96 Some references Books J. Blauert (ed.): Communication Acoustics, Springer, 2005 H. Fastl, E. Zwicker: Psychoacoustics. Facts and Models, Springer, 2007 S. A. Gelfand: Hearing. An Introduction to Psychological and Physiological Acoustics, informa healthcare, 2010 D. M. Howard, J. A. S. Angus: Acoustics and Psychoacoustics, Focal Press, 2009 Suzuki et al: Principles and Applications of Spatial Hearing, World Scientific, 2011 T. Poulsen: Psychoacoustic Measuring Methods, Lecture notes, Ørsted DTU, Acoustic Technology, 2007 Rodrigo Ordonez: Lectures on psychoacoustics, Workshop for COST action TU0901,

97 Some references Journal papers N. Otto, S. Amman, C. Eaton, S. Lake: Guidelines for Jury Evaluations of Automotive Sounds, Sound and Vibration, April 2001 S. Zielinski, P. Brooks, F. Rumsey: Of the Use of Graphic Scales in Modern Listening Tests, 123 rd AES Convention, Paper 7176, 2007 S. Zielinski, F. Rumsey: On same Biases Encountered in Modern Audio Quality Listening Tests A Review, JAES, Vol. 56, No. 6, , 2008 S. Zielinski: On same Biases Encountered in Modern Audio Quality Listening Tests (Part 2), JAES, Vol. 64, No. 1/2, New Horizons in Listening Test Design, JAES, Vol. 52, No. 1/2, 65-73,

98 Some references Journal papers Tutorial Seminar: Listening Tests in Practice, Chairman: N. Zacharov AES 115 th Convention, , 2003 Head Acoustics: Psychoacoustic Analyses I, Application Note 10/16 Head Acoustics: Conducting Listening Tests, Application Note 98

99 Thank you for your attention hope you could hear something new! 99

100 Overview of the hearing process Sound reproduction systems Acoustic comfort Psychoacoustics and psychoacoustic parameters Listening tests Examples (case studies) 100

101 Which sound reproduction system should we use? Complete frequency spectra Complete hearing dynamic range without distortion All information about the direct sound, first reflections, diffuse field The sweet spot as large as possible Different systems have different areas of proper sound source localization 101

102 Binaural systems Most natural sound reproduction system, only 2 channels Using HRTF (Head Related Transfer Functions) for auralization purposes 102

103 Binaural systems But, only individual reproduction possible Non-individual HRTF s, front-back confusion Head tracking and real-time binaural syntehsis 103

104 Binaural systems In-between alternative use of loudspeakers for binaural reproduction, with crosstalk cancellation (CTC) algorithms 104

105 Stereo(phonic) systems Use of amplitude panning for positioning sound sources Speaker angular distance has to be modest! 105

106 Stereo(phonic) systems The development of cinema audio systems was the initiator of surround sound innovation 106

107 Stereo(phonic) systems New systems with encoded height information Object based systems! VBAP: 107

108 Coherent and homogeneous systems System with stable sound image also by position and head movement change; no direction is preferred by the system (unlike home cinema) Acoustic holography recreation of the sound field Ambisonics and Wave Field Synthesis (WFS) systems 108

109 Ambisonics systems Sound field decomposition to spherical harmonics 109

110 Ambisonics Soundfield microphone 1 st order ambisonics recording with 4 capsules Up to 3 rd order recording with Eigenmic (32 capsules) 110

111 Ambisonics encoding and decoding Example of sound source circling in the horizontal plane within the ambisonics system 111

112 Ambisonics 112

113 Wave field synthesis Based on Huyghens' principle - propagation of a wave can be formulated by adding the contributions of all of the secondary sources positioned along a wave front 113

114 Wave field synthesis 114

115 Virtual reality systems CAVE = Computer Aided Virtual Envirnoment Visual 3D space (goggles), Audio 3D space usually rendered using HRTF (Head Related Transfer Functions) 115

116 Comparison of sound reproduction systems limitations mono stereo 5.1 Ambisonics WFS binaural azimuth lim elevation no no simulated yes no for 2D yes head movement yes limited limited yes yes no source close to head no no no yes yes yes distance no simulated limited yes yes yes spacial impression no simulated limited yes yes yes sound envelopment no no limited yes yes yes 116

117 Overview of the hearing process Sound reproduction systems Acoustic comfort Psychoacoustics and psychoacoustic parameters Listening tests Examples (case studies) 117

118 Acoustic comfort RT ~ 1 s STI ~ 0.55 RT ~ 3 s STI ~ 0.40? C80... G Leq??? C80... G Leq??? 118

119 Acoustic comfort 119

120 Acoustic comfort Noise levels Speech intelligibility Acoustic comfort Sound insulation Reverberance/ spaciossness 120

121 Acoustic defects > 17 m 121

122 Auralization standpoint importance! 122

123 Summary! P1 1 Odeon Licensed to: Unversity of Zagreb, Croatia 123