There are three auditory functions that are critical in the context of designing a user interface for older people:

• Sound detection is the ability to hear various loudness of sound, and the ability to hear sounds at certain frequencies.
• Contrast sensitivity is the ability to discriminate between sounds, particularly when speech and background noises are involved.
• Spatial localization is the ability to tell where a noise is coming from, and distinguish between foreground and background sounds.

Age-related hearing loss (Presbycusis) is one of the most common conditions affecting older adults, second only to arthritis in terms of the number of seniors affected.  According to the US National Institute on Deafness and Other Communications Disorders approximately 33% of people in the United States between the ages of 65 and 74, and 50% of those older than 75 have significant hearing loss.  Some studies state that this number grows to 93 percent for people over 81 years of age.  These are important considerations when designing a user interface for older people.

Hearing declines in predictable ways as we age.  Most commonly, it arises from changes in the inner ear, but it can also result from changes in the middle ear, or from complex changes along the nerve pathways from the ear to the brain.  Certain medical conditions, medications and smoking history may also play a role.

One cited recommendation for age-related hearing loss is to require at least 90 dB loud sound for notifications (70 dB is recommended for younger users); and the level of an alarm should be at least 10 dB above the background noise, otherwise it may not be heard.  Note, however, that as a rule, a sound that is uncomfortably loud for someone with normal hearing will also be uncomfortable for older people with hearing loss.

Beyond difficulty with hearing low volume sounds, older people find it harder to hear high pitched sounds (e.g., some female voices, certain speech sounds and high musical notes).  Some seniors also find it harder to detect very low pitched sounds.  And it is harder for older ears to distinguish noises at similar frequencies which may sound blurred when close together (pitch and frequency are synonymous).

Elderly adults may also find it harder to work out the spatial location of a sound.  In addition to difficulty in telling where a sound is coming from, there is difficulty distinguishing between foreground and background noises.  This important in a user interface for older people.

Older people are more likely to suffer from Tinnitus, which is hearing noises in the head (not related to any psychiatric condition) which interfere with external sounds.  Some people describe tinnitus as high-frequency whistling sounds while others perceive tinnitus as a buzzing noise or a sound similar to butter sizzling in a frying pan.  The most common cause of tinnitus is exposure to noises that are either too loud or last too long.  In today’s baby-boomer population, the cause is often a lifetime of loud music.

Elderly people find it harder to make sense of speech when there is competing speech or background noise (environmental or Tinnitus).  They are less able to deal with fast speech.  They may depend on extra information from lip movements to make sense of speech.  And older adults are slower to respond to sound cues.  These are all factors which need to be considered when creating instructional audio and video files for older people.

Try the audio simulations below to hear various degrees of hearing loss in a train station setting where directions are being provided in a high background noise setting.  Set your speaker volume for the “Normal Hearing” clip at the lowest comfortable level.  Then play the three other clips to simulate increasing degrees of hearing loss.

Train Station – Normal Hearing

Train Station – Mild Hearing Loss

Train Station – Moderate Hearing Loss

 Train Station – Moderate to Severe Hearing Loss

Simulations Produced Using the  Hearing Impairment Simulator

Understanding of hearing is critical to the new voice recognition technologies, and voice activated assistant products, being introduced by Microsoft, Google, Apple, Samsung, and others.  These all provide audio feedback to questions and commands.  Hearing and sounds are also important in other digital user interfaces such as those in home appliances, automobiles, wearable products, kiosks, elevators, etc.

Mitigation Strategies:

• Provide captions with videos and text transcripts of audio files. If captions are displayed, use static text rather than moving text in a user interface for older people (see the Vision section).
• Include a sign language interpreter in video streams. If possible use an elderly interpreter.
• Provide easy to understand and use adjustable tone and volume levels where possible. Do not expect many older people to find the standard (often hard to find) settings provided by standard device operating systems.  Your user interface should make such settings obvious and easy to use.  For example, provide proxy sound controls directly in your user interface that change the related operating system or browser settings.
• If you cannot provide adjustable tone and volume levels, then ensure sufficient loudness given the expected ambient noise level in a user interface for older people.
• Filter out background sounds and noises. When not possible, mix audio files so that non-speech sounds are at least 20 decibels lower than the speech audio content.
• Consider using sounds with multiple frequencies to help people determine where the sound is coming from and to distinguish between background and foreground noises.
• Audible user interface notifications should be at least 90 dB for seniors with hearing loss (70 dB is the normal value for younger people). Audible user interface alarms should be at least 10 dB above the background noise.  But avoid uncomfortably loud sounds.
• Ensure that the frequencies of beeps, tones and alarms are within the range 800 to 1000 Hz in order to maximize the number of people able to detect them. Avoid very high or very low frequencies.
• Avoid high speed and high pitched speech in your user interface for older people.
• Where possible use natural speech rather than synthesized speech.
• Use intonation, appropriate word rate and clear pronunciation to help understanding of speech.
• Use age-appropriate vocabulary in your user interface for older people.
• Where possible augment speech with graphics to assist understanding of speech in your user interface for older people.
• Ensure that systems which transmit and reproduce sounds and speech do so with sufficient clarity.
• Utilize assistive technologies that might help accommodate hearing impairments (e.g., speech to text software). Also consider using haptic (vibration or other tactile) feedback when an action is taken or an event occurs in the user interface.  Be aware of possible information overload when multiple assistive technologies are employed.
• Include information on “TTD/TTY” services when listing telephone numbers for seniors.
• Consider providing inductive couplings to assist communication with hearing aids.

Below are some hearing tools and resources that can assist user interface designers:

• The iOS Hearing Loss Simulator allows you to choose a specific hearing loss configuration and then listen to sounds as though you have that particular hearing loss.
• The Impairment Simulator Software simulates various degrees of hearing loss. This can help to provide insight into the impact of hearing conditions (best used in Internet Explorer).

• The HearLoss software allows the user to adjust a range of hearing parameters and hear the effect on their own audio files.
• The NIOSH Hearing Loss Simulator allows a you to hear and visualize the effects of noise exposure. Estimates of the effects of different levels of noise exposure are based on the American National Standard Determination of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Impairment, otherwise known as ANSI S3.44.