Cornell University Ergonomics Web

DEA 3250/6510 CLASS NOTES

Auditory Displays and Cutaneous, Olfactory, and Taste Information

Auditory Displays - Auditory information displays are commonplace in the speech we generate and hear, the radios/music we listen to, the TV's we watch, etc.

1. Advantages of Auditory over Visual - Using the auditory modality offers several advantages over visual displays (or when to use Auditory displays):
a. When the origin of a signal itself is a sound.
b. When the message is short.
c. When the message need not be referred to at a later date.
d. When the message deals with events in the time, e.g. cassette player in a museum to guide you through.
e. When the message calls for immediate action, e.g. starter gun at a race.
f. When the visual system is on overload, e.g. a pilot with a warning sounds from instruments.
g. When illumination limits vision.
h. When the position of the receiver varies.
i. When a verbal response is required.


2. General Principles -
a. Compatibility - Make use of pre-existing stimulus-response relationships which may be natural, learned, or population stereotypes.

(1) Orienting reflex - is a basic reflex to turn to the source of a sound (stimulus), e.g. If you want an auditory sound as a warning for a pilot, don't put the speaker behind her!

(2) Learned - Examples are sirens which are learned to be associated with an emergency; higher frequency = high value like a tea kettle whistle.

b. Approximation - Complex messages should be presented in two stage signals:
(1) Attention Demanding Signal - to capture attention.
(2) Designation Signal - with precise message information.

c. Dissociability - Auditory signal must be discernible from other noise, especially multiple auditory signals, e.g. when several phones ring in an office it's difficult to tell which is ringing.

d. Parsimony - Messages should be as short as possible.

e. Invariance - Same signal or message should designate the same information in all situations to avoid confusion like that between "priority" and "emergency" information.

3. Presentation of Auditory Information -

a. Avoid extreme auditory dimensions - if sound is too loud or there will be a "startle response".

b. Signal/noise ratio - Establish intensity relative to ambient noise levels to avoid masking.

c. Variable Signal - An interrupted or variable signal works best to attract attention by minimizing perceptual adaptation to monotones and increasing the delectability of the signal, e.g. Beep! Beep! Beep! is better than "Beeeeeeeeeep"!

d. Don't overload the auditory channel - you need to know something about the situation and consider the effect of the auditory information on the whole system.


4. Warning Signals - Auditory displays are especially useful for signaling alarms partially because noise will go around corners. "Yeows" and "Beeps" get a faster response time.

5. Using Auditory Displays Effectively -
a. Use frequencies between 200 - 5 Khz. Preferred range is between 500 and 3 Khz the most sensitive range for hearing.
b. Use frequencies below 1000 Hz when the signal has to travel more than 1000 feet.
c. Use frequencies below 500 Hz when the signal has to pass through partitions or "bend around" obstacles.
d. Use modulated signal (1 - 8 beeps/ sec, warble 1 - 3/sec)
e. Use signals with frequencies different from background noise to avoid masking.
f. For choice situations, use moderate intensity easily discriminable frequency or amplitude signals ( but not too many).
g. Where possible use separate auditory warning system which is different from other auditory signals.


Cutaneous Information

1. Using Cutaneous Information - Touch can be used as sensory replacement in many ways. Used to guide people when the lights go out. Controls can be shaped differently. Things can be more or less desirable by feel.
a. Methods - Cutaneous senses can be engaged through texture, tactile display (haptic),
shape, vibration - vibro-tactile display - small pins that vibrate, or electrical means through a mechanical or electrical transducer

2. Pacinian corpuscles - Receptors that sense changes in the skin, (heat, etc.). They are not equally distributed over the body. Highest density is at the tips of the fingers. Different parts of the body have different receptors


3. Tactile Graph Presentations - Some possibilities are: Braille line graphs,
How does a blind person interact with an ATM?
See Figure 6-16 in text - discriminable area symbols for use on maps
ex. volume switch, on/off - if you're blind how do you tell the difference?
What do you do when vision is going to be limited? Coding systems for controls - size, shape, position etc.

Olfactory and Taste - Olfactory displays haven't yet been used for many applications.
1. Olfaction - Examples: natural gas is odorized for safety; mine safety systems are often "stench systems"; increase or decrease product desirability.

2. Taste - Examples: medicine; toys, pen tops (so children don't swallow them and die); scratch and sniff products; Japanese companies introduce odors into offices; air fresheners only add odorous chemicals into the air; and human pheromones.

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