Auditory, Tactical, and Olfactory Displays ECE 796/896 Chapter 6 Auditory, Tactical, and Olfactory Displays

Hearing Frequency and intensity Frequency ( 20-20,000 hertz) Intensity = loudness

Anatomy of an Ear Three divisions, outer ear, middle ear, and the inner ear. Outer ear: collects sound energy Eardrum is at the end of the auditory canal in the outer ear.

Cont… Middle Ear: Separated by the eardrum from the outer ear. Inner Ear: spiral-shaped about 30 mm long. Filled with fluid transfers. movement to basilar membrane which transmits movement to organ of corti.

Sound Waves to Sensation How we “hear” sounds. Place Theory: fibers along the basilar membrane act like piano strings. Temporal Theory: pitch is related to the time pattern of impulses transmitted by the fibers. Complementary model using both theories.

Cont. The ear is not equally sensitive to all frequencies of sound. Less sensitive to (20 - 500 Hz) More sensitive to (1000-5000 Hz)

Masking One sound covered by another. The extent by which the audibility threshold is raised in the presence of another. The most masking occurs nearest the original frequency and its harmonics. Also the greater the intensity of masking tone the greater its effect.

Auditory displays From chapter 3 - auditory displays preferred Origin of the signal is a sound Message is simple and short Message will not be referred to latter Message deals with events in time Warnings or immediate action Continuously changing information is presented Visual system is over-burdened Speech channels are fully deployed Illumination limits vision Receiver moves Verbal response is required

Reception of auditory signals 1. Detection 2. Relative Discrimination 3. Absolute Identification 4. Localization

Detection of signals Filters: most effective when the noise and signal are vastly different. Increasing detectability:reduce noise, increase the signal, present signal for .5 to 1 sec., change freq. to a noise free region, phase shift signal in one ear, and present noise to both and signal to one ear. Finally, use complex sounds in the 1000 - 4000 Hz.

Relative discrimination of Auditory Signals JND: Just noticeable difference - The smallest change in sound that can be noticed by 50% of the people. The smaller the JND the easier it is for people to detect the differences on the dimension.

Discriminations of Intensity Differences The higher the intensity the smaller the JND. (at least 60DB above the threshold) JND are smallest (1000-4000 hz)

Multi-dimensional coding If the information to be transmitted by auditory codes is substantial, then multi-dimensional coding could be required. Right vs. left ear, intensity,frequency, rep. rate, on/off time, and duration.( each dimension needs to have few steps)

Sound Location Sterophony: the ability to localize the direction of sound waves. Differences between intensity and phase. Low frequencies make location difficult, higher frequencies are easier.

Cont. Conclusions: Auditory system is insensitive to motion Detection of simulated sound movement is worse than detection of real sound movement Detection of broadband noise is easier

Principles of auditory Display 1. General Principles: Compatibility, Approximation, dissociability, Parsimony,Invariance 2. Principles of Presentation: Avoid extremes of auditory dimensions, establish intensity relative to ambient noise level, use interrupted or variable signals, do not overload audio channel 3. Principles of installation of auditory channel: Test signals to be used, avoid conflict with previously used signals, facilitate changeover from previous display

Special Purpose Auditory Display Warning and Alarm Systems Frequencies (200-5000 Hz) For long distance signals use Frequencies below 500 Hz Modulated signal (1-8 beeps per sec) - warbling between 1-3 per sec Signal should use frequencies that are different from background noise Use separate communication system for signals

Aids for the Blind Pathfinder Single-object Sensor Sonic Pathfinder Sonic Guide

Cutaneous Senses Classified qualitatively by stimulus (thermal,mechanical,etc.), anatomically (nature of sense organs) Three separate sense systems, pressure perception, one for pain and for temperature sensing. Sensitivity to touch - two point threshold

Tactual Displays Substitutes for Hearing: reception of coded messages, perception of speech, and localization of sound. -send MORSE code

Identification of Controls Display design incorporating different types of knob designs. Reading Printed Material - Braille Opticon - optical-tactile conversion Navigation Aids: Features are classified into point features(bus stop), linear features(road), areal features(park)

Cont. Tracking task Displays

Olfactory Displays Gas company - adding odors