Chapter 5 Auditory System.docx

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Management and Organizational Studies
Management and Organizational Studies 3305A/B
Suzanne Kearns

Chapter 5 AUDITORY, TACTILE, AND VESTIBULAR SYSTEM September 18, 2013 SOUND The Auditory Stimulus  The stimulus of hearing is sound  Sound o A vibration of air molecules o Represented as a sine wave o Characteristics of sound  Amplitude Corresponds to loudness  Frequency Corresponds to pitch  Location Source of sound relative to hearer  Envelope (temporal characteristics)Distinguishes wiling of a siren from stead car horn Decibels  Amplitude is expressed in decibels (dB) o Decibels represent sound in 2 ways  Ratio – sound: threshold of hearing  Vacuum 80  Subway 100  Propeller 120 (hearing loss)  Jet 140 (threshold of pain)  Ratio – hearable sound: hearable sound (ambient noise)  Better ratio – relative, makes sense  Eupnoea direct sound into inner ear  Eustachian tube connects ears to mouth and noise O Equality air pressure between the two  Hammer/anvil/stirrup are 3 bones amplify sound  auditory nerve  brain  Bony cochlea transfer sound ALARMS  Designing good alarms depends on good understanding of auditory processing  Why is an auditory horn better than a visual alarm?  Auditory system is o Omni-directional o More difficult to close ears than eyes o Auditory alarms induce greater compliance  If an alarm MUST be recognized, it should be auditory o Redundancy in visual OR tactile channel is beneficial (i.e. redundancy = horn AND buffeting for stall) GOOD &B ADALARMS  Alarm must be heard o At least 15dB (higher than ambient noise)… 30dB difference should guarantee audibility o Should contain variable frequencies (older people might not hear)  Alarm should not be above the danger threshold of human hearing… 85-90dB  Alarm should not be overly startling  Alarm should not overwhelm necessary communication o Example of poor design: helicopter rotor (engine failure) and radar altimeter sound too alike  Alarm should be informative & consistent in nature Voice Alarms Advantages Disadvantages  Exact meaning  More confusable with background noise  Listener not familiar with the language  Easier to mislead Solution  Use a redundant system o Combine speed + non-speech components o Whoop! Whoop! Pull up! Sound Localization  Ability to process sounds is better in azimuth (left-right) than elevation o Ears are on the side of your head… lol  Front-back confusions are prominent o Cone of confusion  Both ears receiving info at same time… can’t differentiate source o People naturally accommodate by turning head  Overall, precision is less than in visual localization  Sound localization can provide value o When visual field is already cluttered o When objects approach from 360 degrees  Visual field is only 130 degrees Auditory Masking  One sound covers up another sound  Masking potential depends on o Intensity (loudness) o Frequency (harder for bad hearing to hear female voice – higher frequency)  Variables include o Gend
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