Chapter 5. Sound Intensity (db) = 20 log (P1/P2)
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Transcript of Chapter 5. Sound Intensity (db) = 20 log (P1/P2)
![Page 1: Chapter 5. Sound Intensity (db) = 20 log (P1/P2)](https://reader035.fdocuments.net/reader035/viewer/2022062304/56649e035503460f94aee342/html5/thumbnails/1.jpg)
AUDITORY, TACTILE, & VESTIBULAR SYSTEM
Chapter 5
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Sound: The Auditory Stimulus
Sound Intensity (db) = 20 log (P1/P2)
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The Ear: The Sensory Transducer
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Four Dimensions of Sound
Loudness (intensity)
Pitch (frequency)
Perceived Location
Quality (set of frequencies and envelop) Timbre – what determines the sound of a
trumpet from a flute
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Loudness & PitchPsychophysical Scaling
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Loudness & PitchFrequency Influence
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Loudness & PitchMasking
Sounds can be masked by other sounds Principles of masking:
The minimum intensity difference to make sure that a sound can be heard is around 15db above the mask
Sounds tend to be masked most by sounds in a critical frequency band surrounding the sound that is being masked
Low-pitch sounds mask high-pitch sounds more than the converse. e.g., a woman’s voice is more likely to be masked by other male voices than other female voices masking a man’s voice even if both are speaking at the same intensity
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Alarms
Alarms are normally auditory because hearing is omnidirectional and it is much easier to close our eyes than our ears
However auditory alarms have there draw-backs when not properly designed
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Design Criteria for Alarms
Must be heard above background noise Intensity should not be above the danger
level for hearing when possible The alarm should not be over startling The alarm should not disrupt other the
processing of other signals or other background speech communications
Alarm should be informative to the listener on what action to take – fire alarm to cause building evacuation based on previous knowledge
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Alarm Design Approach
Perform environmental & task analysis to understand quality & intensity of other sounds (noise or communications)
Try to stay within the limits of absolute judgments
Design warning structure/rational To avoid confusion consider voice alarms
– two concerns are masking by other voice communications and language of listener Make redundant with auditory alarm
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Alarm Structures
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False Alarms
Consider consequences of missing a true warning condition versus a false alarm
Too many false alarms can cause lack of appropriate response Try to improve sensitivity of alarm system Train users to inevitability of false alarms, but
to always respond as if it were true Install multi-level alarm system – e.g., weather
warning
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SOUND TRANSMISSION PROBLEM
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Speech SignalSpeech Spectrograph
Masking Effects of Noise: Potential for masking dependentintensity and frequency of the noise
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Measuring Speech Communication Degradation Associated with Noise
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Speech Distortions
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Correcting Speech Distortions
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Hearing Loss
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Noise Revisited
Potential Health Hazard Potential Environmental Irritant
Loss of sensitivity while noise is present Permanent hearing loss Temporary threshold shift
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Noise Remediation
Signal Enhancement Noise Reduction
The source: equipment and tool selection The environment The listener: ear protection
Environmental Noise Is all noise bad? No (background music
to mask irritating ticking or conversation distractions)
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Other Senses
Touch: touch (pressure) and haptic (shape) senses Problems – surface membranes, gloves,
shapes, spatial/symbolic information, & virtual environments
Proprioception (brain’s knowledge of finger position) & Kinesthesis (brain’s knowledge of joint motion)
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Tactile/Haptic Sense Illustration
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Vestibular Senses
Three semicircular canals act like three gyros in early navigation systems