Term
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Definition
•Acoustic information can come as:
o Noise (unwanted)
o Alarms (wanted)
o Speech (wanted)
• All 3 are important for:
o System Performance
o Human Performance
o Safety
o Health |
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Term
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Definition
• Stimulus for hearing is sound
• Sound is heard because of a change in pressure (eg. Air) sensed by the ear due to vibrations of some source
• Sound intensity is measured in terms of pressure on a decibel (dB) scale |
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Term
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Definition
• Amplitude (intensity)
• Frequency (measured in cycles/second or Hertze (Hz)
• Duration
• Location |
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Term
| Perception of sound: Bottom up & top down processing |
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Definition
• Top-down
o Your expectations of what should be there
• Bottom-up
o Sensing what is there
o “hearing what you want to hear” |
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Term
| Sound People can Perceive |
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Definition
• The frequency range for human hearing = 20 Hz - 20,000 Hz
• The sensitivity of human ear drops off below 500 Hz and above 4000 Hz
• Speech occurs in the range of about 200-5000 Hz |
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Term
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Definition
• Equal increases in sound intensity do not create equal increases in perceived loudness
• Loudness is perceived to approx.. double every 10dB
• Frequency also affects perceived loudness
• Loudness is a psychophysiological phenomena |
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Term
| Noise – Performance, Safety and Health (5) |
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Definition
• Masking
• Startle response
• Temporary and permanent threshold shifts (hearing loss)
• Effect on work performance
• Annoyance, stress |
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Term
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Definition
• Noise can prevent people from hearing communications, information signals, or alarm sounds
• Noise (from speech, devices, procedures) can mask sounds
• Masking occurs when one aspect of sound environment reduces the sensitivity of the ear to another component of the sound environment
• Lower frequency sound tends to mask higher frequency sound (more than vice versa)
• Ex) medical professional can identify 96% of breath sounds in quiet environment, but only 54% in an ambulance |
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Term
| Masking - Dealing with Masking |
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Definition
• Increase the signal
• Decrease the noise
• 15db heuristic?? |
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Term
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Definition
• If a noise is too loud or too sudden, can cause a startle
• If a loud noise is prolonged, it may lead to a prolonged stress response
• Bad for tasks requiring concentration or use of fine motor skills |
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Term
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Definition
| • Intense sounds can cause selective hearing loss at frequencies that correspond to cilia at certain locations in the basilar membrane |
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Term
| Factors affecting Hearing Loss |
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Definition
• Sound intensity
• Type of noise (wide band, narrow band, impact)
• Duration of exposure
• Dose
• Protections in place
• Related diseases
• Age (older people) |
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Term
| In Health care studies, noise has been shown to (4): |
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Definition
o Increase lengeth of hospital stay
o Contribute to sleep-wake abnormalities in the ICU
o Increase nurse heart rate, subjective stress, and annoyance
o Possibly impair task performance, concentration, and complex problem solving task performance |
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Term
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Definition
• Loud noise can impair reading comprehension
• Noise also influences response bias
• Noise appears to have little impact on motor performance or sensory functions such as visual acuity, contrast discrimination, dark vision, and accommodation
• High concentration, complex and high vigilance tasks are affected by noise |
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Term
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Definition
| • Increased muscle tension and blood pressure in rxn to noise |
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Term
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Definition
• Auditory alarms tend to be the preferred type of alarm because:
o Omnidirectional
o Harder to close ears than eyes
o Higher compliance than visual alarms |
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Term
| Designers of alarms tend to set criteria low for safety reasons, that can lead to: |
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Definition
o Mistrust of alarms
o Ignoring alarms
o Disabling alarms |
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Term
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Definition
• Touch is complex (ex. Tying a shoelace)
• Only bi-directional communication channel – both input and output
• Provides information about our environment
• Ability to detect skin deformations
• Acuity determined by how close and size of receptive field |
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Term
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Definition
• Of or relating to the sense of touch; tactile
o Involves both proprioceptive and tactile senses in concert with other sense |
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Term
| Olfactory Displays - We don’t use smell as display because: |
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Definition
o Wide variation in sensitivity
o Stuff noses
o Adaptation to smells
o Dispersion of molecules hard to control
o Some smells make people sick |
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Term
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Definition
• Considerations for selecting a non-visual display channel
o If displayed info occurs randomly and must immediately capture attention of operator
o Omni-directional characteristics (sound propagation)
o Information rates (channel specific limitations)
o Method of coding information |
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