By Gary Ferrington

A media designer must not only have a good eye for visual composition but also a good ear when it comes to sound design. Loss of hearing, as with sight, obviously limits one's ability to be an effective designer. Yet so few give attention to the health of their ears.

Hearing impairments can be subtle and easily overlooked. However, if you find that sounds seem muffled, you have difficulty understanding speech, or you hear a continuous ringing or buzzing sound in the ears, this could be evidence of the onset of hearing loss, and you should have your hearing tested. This condition is often caused by exposure to loud sound and the task becomes one of preserving what hearing remains.

Consider, for a moment, the biological purpose for human hearing. Hearing evolved to enhance the possibilities of human survival in a predatory world. The relatively slow running human, having a need to detect danger and flee, evolved the ability hear the quietest of rustling sounds, thus gaining a heads-up as to what may be stalking him or her in the bush.

Now leap forward several thousand years and here we are with ears designed for an environment in which the loudest sound was probably that of a passing thunder storm. In today's soundscape our ears are bombarded with a cacophony of sound. From household blenders, vacuum cleaners, TV sets, to the industrial sounds of our modern world, our ears are assaulted with sound levels for which they never were intended.

The development of sound amplification systems has added to the assault on human hearing, and we who work in media need to give that assault and the resulting loss of hearing serious attention.

The human ear is rather simple in design yet highly efficient. It consists of the outer ear, middle ear and inner ear. Sound waves pass through the outer ear which is designed to funnel sound into the inner chamber where the eardrum is located.

The term eardrum is appropriate. Sound waves bounce against the eardrum and cause it to vibrate - much like the surface of a drum vibrates when hit. Attached to the ear drum are three small delicate bones — the hammer, the anvil and the stirrup. The ear drum, a vibrating membrane, causes the attached hammer bone to strike the anvil which in turn vibrates the stirrup. Up to this point the whole system is very mechanical. But now this process begins to change.

The stirrup is attached to a snail-shaped structure called the cochlea. The cochlea is filled with fluid and thousands of hair-like nerves. The vibrating stirrup shakes the cochlea causing waves of fluid to wash over the nerve endings. As these nerves are brushed against an electrical signal to the brain is generated. The brain interprets these different impulse patterns as sound.

In extremely loud environments some of the hair-like nerves in the cochlea may literally break, or flatten out, thus removing the brain's ability to receive certain auditory information from the ears. Unfortunately, once hearing loss occurs it cannot be restored; the damage is permanent. Some people feel that if their ears don't hurl turing exposure to loud sounds that their ears are fine, but the delicate hearing system can be easily damaged when a tsunami of a sound wave overwhelms it.

It is estimated that 1 in 10 American adults have difficulty hearing according to the National Institute on Deafness and Other Communication Disorders. That is about 32.5 million individuals who are experiencing hearing problems today. Some of this hearing loss can be contributed to the natural process an aging population. But, according to the American Academy of Otolaryngology, there is an increasing number of younger people in their late 20s and early 30s, that are showing early signs of hearing damage much of which comes from listening to loudspeakers and headphones, as well as their living in a generally louder urban environment.

Humans can hear sound within a frequency range needed for the survival of the species of about 20-20,000 Hz. Other creatures have hearing ranges that are much broader than we humans. Dogs, for example dogs can hear frequencies up to 65,0000 Hz. Elephants are able to hear a low rumbling sound of about 5-30Hz ,originating up to 5 miles away.

The loudness of a sound is subjectively perceived and measuring it often depends on how close one is to a sound source and the amount of energy that source is producing. The loudness of a sound is measured using the decibel scale (dB). This scale is logarithm and can be quite complex when different variables are computed. Suffice it to say that the threshold of hearing is listed as 0db and the rustling of leaves is about 20 dB or 10 times higher than the threshold of hearing. The sound of a jet aircraft taking off 200 feet away is 120dB or just below the threshold of pain. The threshold of pain is that level where the loudness of a sound becomes unbearable for a human listener and damage is almost always instantaneous. Although high pitched sounds can damage hearing it is most often the loudness and the length of exposure to a sound source that is the primary cause of noise-induced deafness.

So, how loud is too loud? Somewhere between the threshold of hearing and the threshold of pain the loudness of sound becomes too much for the ear and the bio-mechanical process involved in hearing is susceptible to damage. Most sources identify as dangerous a sound that is 85 dB or higher. Busy city traffic is a noise level at which the hearing mechanism can begin to suffer noise induced hearing loss. Sound levels less than 75 decibels are unlikely to cause permanent hearing loss, but remember exposure to any sound over a period of time can cause hearing fatigue.

A Rock Concert listened to at 10 feet from the stage is the same loudness as a jet aircraft taking off 200 feet away. This level of loudness sustained over time has damaged the hearing of many young people today. Rocker Pete Townsend has been quoted as saying, "I have unwittingly helped to invent and refine a type of music that makes its principal components deaf." In fact the damage to rocker ears has resulted in the formation of an organization called H.E.A.R. or, Hearing Education and Awareness for Rockers.

Those who frequent concert events may also develop hearing loss. The damage many experience today is the same as that once suffered by workers in the boiler industry who hammered on metal all day causing hearing fatigue and eventually diminished hearing. "Boilermaker’s ear", known today, "disco" or "bar" ear, is a serious problem for youth. This condition results in the loss of hearing high frequencies and difficulty, for example, in understanding speech. Exposure to loud music will sometimes result in the listener developing trinities, a condition that is characterized by a high pitched ringing in one's hearing that just won't go away and for which there is no cure. The H.E.A.R. web site has a simple hearing test to take before and after attending a concert that demonstrates the effect of loud sound on hearing.

Not only do concerts create an environment in which hearing may be damaged. The amplification of sound can lead to hearing problems. The popularity of personal audio playback devices has millions of people listening to thousands of hours of music using earphones, often at levels equivalent to rock concerts.

The European Union health guidelines requires that portable listening devices sold in the E.U. not exceed a 100 dB level. Apple, the maker of over 42 million popular iPods has had a maximum sound level capability of 104dB. The iPod was temporarily pulled from French sales and a software upgrade introduced that brought the upper volume level within compliance. Units in America remain capable of the higher dB level. Users who set their volume level to max are listening to the equivalent sound level as that made by a power saw or electrical drill - or louder. Given that 85 dB is recognized as a level at which hearing can be damaged it is obvious that the listener must assume responsibility for preserving his/her ability to hear by turning down the volume down.

A media producer with a hearing impairment is similar to the one who that has limited vision. Both situations greatly hinder a career in audio and visual design. Loosing the ability to hear a full range of frequencies and the possible development of tinitus causes several problems for the designer:

• What may have once been good critical listening skills are weakened when it becomes extremely difficult to hear certain frequencies and tonal colors.
• The ability to be discerning, or having keen aural judgment about the placement and balance of multiple sounds within a design is diminished with hearing loss.
• Hearing the spatial dynamics of a soundscape is diminished when one looses the ability to hear a full frequency range. Such loss is natural over time, but young sound designers may be loosing this ability at an earlier age given the loud acoustic environments in which they participate.
• Very quiet sounds such as tape hiss are often missed. The internal sounds created by tinitus often dominate the aural field so that distracting sounds in a recording are not heard and given attention.
• Hearing impairment may lead to incorrect decisions about volume levels and balance. For example music or sound effects might overpower the narration, or they are weakly articulated as important elements in the design.
• The inability to clearly hear recorded narrative or conversations can create issues in the editing process.
• A designer's hearing is important when presenting a program to a client. Setting the audio playback settings improperly will detract from the content of the program. The desired message becomes modeled for the audience.
• Given that hearing loss usually involves the loss of high frequencies the designer may compensate by leaving a sound thin and harsh on the ears. Sounds may lack a sense of depth.
• Recording in the field is difficult enough with natural soundscape issues that are only exacerbated with a hearing impairment.

The primary cause of hearing loss within our profession is the improper use of headphones. Headphones provide for the isolation of sound and the ability to give it attention by the sound designer. Many, however, tend to listen with the volume levels set higher than that which is healthy for good hearing. It has been noted that those who use headphones are susceptible to decreases in sensitivity to volume levels over time as the ears fatigue. The user compensates by increasing the volume. This cycle is repeated until the headphone "speakers" are blasting sound at an unacceptable level directly into the ears.

Here are some tips gleaned from the literature on headphone use that will help you prevent serious hearing loss.

• Set the volume level for your headphones to less that 75 decibels. Keeping the volume as low as possible without having to strain to hearing sound is best. If co-workers can hear sound emitting from your headphones you have the volume too loud.
• Take a break every 30 minutes. Let your ears relax for a couple of minutes and give yourself a longer break of 5-10 minutes every few hours. It is advised that after four hours one take an hour break.
• Limit the ambient sound in your working environment which competes with the sound project on which you are working through your headphones. Turning up the volume for your head set is not the solution to canceling out background sound.
• Also, check your hearing at least once a year. Hearing loss can be subtle and early detection is important.

Also protect your hearing while doing everyday activities.

• Use your fingers to plug your ears when an emergency vehicle passes you by on the street. The high pitch of the siren and volume level can damage hearing.
• Keep your ears protected by using ear plugs or other protection gear. Don't use leaf blowers, lawn mowers and other noise producing equipment without both ear and eye protection. And, always cover your ears when walking by areas in which such equipment is being used by others.
• Quieting the acoustic environment in general would do much to help retain the ability to hear over a life time.

References:

• H.E.A.R. Hearing Education and Awareness for Rockers. A non-profit hearing information source for musicians and music lovers.
• Lower The Volume! By Dr. Ranit Mishori. Parade Magazine article on noise and loss of hearing.
• Headwize. "Preventing Hearing Damage When Listening With Headphones." A guide to headphone use.
• How to Select & Use Headsets. UCLA Ergonomics.

Special Thanks:

• Josh Taylor, media designer.
• Nigel Frayne, Chair, World Forum for Acoustic Ecology
• Donald Strike, Don Strike Business Training Connections

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