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

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

4. 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.

6. 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.

7. 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.

8. Cont. The ear is not equally sensitive to all frequencies of sound.
Less sensitive to ( Hz)
More sensitive to ( Hz)

9. 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.

10. 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

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

12. 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 Hz.

13. 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.

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

15. 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)

17. 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.

18. 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

19. 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

21. Special Purpose Auditory Display
Warning and Alarm Systems
Frequencies ( 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

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

24. 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

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

27. 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)

29. Cont.
Tracking task Displays

31. Olfactory Displays
Gas company - adding odors