산업경영공학과 IMEN 315 인간공학 5. Auditory System SOUND: THE AUDITORY STIMULUS  sound – a vibration of the air molecules  a sine wave with amplitude (loudness) and frequency (pitch)  sound intensity (dB) = 20 log (P1/P2)  two other temporal characteristics: envelope and location

산업경영공학과 IMEN 315 인간공학 THE EAR: THE SENSORY TRANSDUCER 고막

산업경영공학과 IMEN 315 인간공학 THE AUDITORY EXPERIENCE Loudness and Pitch  psychological loudness not identical to physical intensity – psychophysical scale of loudness and the modifying effect of pitch Psychophysical Scaling qthe scale that relates physical intensity to the psychological experience of loudness, expressed in units called sones, in fig 5.3fig 5.3 Frequency Influence qthe range of human hearing around 20 to 20,000 Hz (most sensitive around 40 Hz) – fig 5.4fig 5.4 ALARMS qthe auditory system is omnidirectional qmuch more difficult to “close our ears” than to “close our eye” qalarm signal that must to be sensed  should be an auditory form

산업경영공학과 IMEN 315 인간공학

산업경영공학과 IMEN 315 인간공학 Criteria for Alarms 1.must be heard above the background ambient noise – at least 15dB above the threshold – 30-dB above to guarantee detection 2.Should not be above the danger level for hearing around 85 to 90 dB

산업경영공학과 IMEN 315 인간공학 3.should not be overly startling or abrupt 4.should not disrupt the perceptual understanding of other signals or any background speech communication – careful task analysis 5.should be informative Designing Alarms 1.environmental and task analysis must be undertaken 2.pitch, envelop, rhythm, timbre of the sound 3.designing the specifics of the individual sound

산업경영공학과 IMEN 315 인간공학 Voice Alarms and Meaningful Sound 1.More confusable with a background of other voice environments 2.More susceptible to frequency-specific masking noise 3.Care must be taken in a multilingual environment qRedundant system qAuditory icons or earcons NOISE REVISITED qnoise as a factor disrupting the transmission of information qnoise as a health hazard in the workplace and as an irritant in the environment qthree components of the potential hearing loss 1.masking – a loss of sensitivity to a signal 2.temporary threshold shift (TTS)

산업경영공학과 IMEN 315 인간공학 3.permanent threshold shift (PTS) – occupational deafness – pronounced at higher frequencies around 4000 Hz NOISE REMEDIATION Signal Enhancement qnoise level below 85 dB – signal enhancement procedure qabove the action level – noise reduction procedure

산업경영공학과 IMEN 315 인간공학 Signal Enhancement 1.careful consideration of the spectral content of the masking noise 2.redundancy associated with top down processing – face-to-face mode, use of the phonetic alphabet, the choice of vocabulary Noise Reduction in the Workplace The Source: Equipment and Tool Selection qDamping material, such as rubber The Environment qPath from the sound source to the human qShields, sound absorbing walls, ceiling The Listener: Ear Protection qearplugs, ear muffs, noise reduction ration (NRR) qearplugs offer greater overall protection if properly worn qmuffs better for signal enhancement and noise reduction

산업경영공학과 IMEN 315 인간공학 Environmental Noise qmore irritating for high frequencies, airplane noise, nighttime noise, noise in summer THE OTHER SENSES Touch: Tactile and Haptic Senses qsensory receptors under the skin respond to pressure on the skin qalong with the sensation of pressure, tightly coupled with the proprioceptive sense of finger position, also provide haptic information Proprioception and Kinesthesis The Vestibular Senses qtwo sets of receptors in the semicircular canal and in the vestibular sacs (illusion and motion sickness)