Understanding HCI

Audio

What is hearing?

  • Hearing is the second most important sense in interface dedign.
  • Hearing is a response to air particles that are displaced at a distance from us.
  • Although each particle only moves a tiny fraction, this causes a series of successive variations in pressure. When these sound waves reach the ear, they trigger a series of mechanical pressure changes, which eventually trigger the auditory receptors, causing the sensation of hearing.
  • Sound waves vary in
    • amplitude (the height of the wave crest),
    • wavelength (the distance between each wave crest) and
    • the frequency (the number of waves per second, measured in Hertz).
  • The loudness of a sound is described in decibels.
  • Sound is a good way of attracting attention, since people respond more quickly to auditory signals than to visual signals.

Design considerations for Audio

Use the sound system for alerts when:

  1. The information is short and simple
  2. The information will not be referred to later
  3. For alerts which require the users immediate attention
  4. The users visual system is already overburdened
  5. The user is moving about from place to place
  6. Poor illumination makes vision unreliable

sense of place

  1. Sound can also be used to give the user a sense of place - especially important in virtual reality environments, variations in sound can give users a sense of movement by using the Doppler effect - sound waves hit the eardrum successively faster as the object approaches and then once it has passed, the sound waves get progressively further apart (imagine an ambulance or train passing by as you stand still).
  2. Sound as used in interface design has been described as:
    1. earcons - brief structured non-speech sounds which can be regarded as musical (ding)
    2. auditory icons - everyday sounds mapped to computer events by analogy are not musical (door slam)
  3. For visually impaired individuals, Auditory Display (AD) can play a part in making interfaces available to them which were previously inaccessible.

Examples

some simple animations which use sound to good effect - http://www.lycettebros.com/notmytype/index.htm

Limitations Of Sound

  1. Many people find repeating sounds annoying
  2. there are no guidelines for auditory aesthetics but suggestions include
    1. ensuring competing sounds are harmonic and melodic
    2. use of fade-in and fade-out to soften sound transitions
    3. limiting the use of sound density

Exercise

Exercise 1

Choose 1 of the animations above and in small groups of 2 or 3 answer the following:

  1. list and describe the different types of sounds used
  2. what is the function of these sounds?
  3. how does the sound work to give the audience a sense of place?
  4. are there any which are particularly effective? why?
  5. are there any which are ineffective? why?
  6. are fades used to soften sound transitions?
  7. view the animation with the sound off - how is your experience effected?
  8. should the emotional potential of music be used in auditory interface design?
  9. can we design emotionally neutral sounds?

Exercise 2

Consider an Auditory Display ATM machine

  1. Who would this benefit?
  2. What potential problems do you envisage with implementing this?
  3. How could you solve these problems?

Exercise 3

Read sections 3, 4.1, 4.2, 4.3 of the reading below.

  1. Can you suggest an alternative method of denoting 'attachment types' to that in 4.2 part 4 and 4.3 part 4.

Reading

How to tackle auditory interface aesthetics? Discussion and case study.