Currently viewing Vol. 1 • Issue 4 • 2014

Common Transient Sounds: The Kitchen is a Very Noisy Place

Stories from Our Past

Wayne Staab, PhD (and official Canadian Audiologist Audiology Historian) and Robert Traynor, PhD will alternate Stories from our Past which are about technical innovations and approaches that are now ubiquitous in our field or were important in the development of our field. In many cases, these stories will be written by the innovators themselves.

Reprinted with kind permission from The Hearing Review, January 1995

The clatter of dishes and silverware is frequently cited in professional literature as a source of annoyance for hearing instrument users. As a longtime hearing instrument wearer, I could only smile in rueful recognition when told by an audiologist friend that “many of my male clients believe that their wives torture them deliberately by needlessly banging dishes and pots and pans in the kitchen,”1 I had often thought that my wife, otherwise the gentlest of souls, seemed to be uncharacteristically rough with her kitchen utensils. Couldn’t she just handle them more carefully?

Just how loud are those irritating sounds? While information on other everyday noises has been published,2,3 no systematic data on the “dishes, pots, and pans” family of noise-makers appears to be available. Killion4 briefly mentions that a spoon dropped on a plate produces 110-115 db, but that is the only reference I have found.

Measuring the Noise

During the 1987 World Series in Minneapolis, CNS News used a sound level meter (SLM) in the Metrodome and measured a hometown crowd cheering the Twins at up to 120 dBA sound level. Much was made of that number as being an extremely loud sound, equivalent to a jet aircraft on takeoff power at a distance of 200 ft.

My initial venture into the kitchen with a meter produced numbers not nearly as impressive. A reading of 70-75 dBA during some vigorous operations with pots on the stove about equaled the normal sound levels in a moderately noisy restaurant.2 I knew this should not be unduly bothersome yet the sounds were sharp and irritating. Since the SLM is an averaging device, could it be missing the sharp peaks I was hearing?

A digital oscilloscope connected to the SLM revealed that this was indeed the case. The instantaneous peaks produced during meal preparation and dish-handling activities usually exceeded 80 dB and frequently reached 90 dB in the breakfast nook area – nine feet from the scene of the action. When the SLM was right by the kitchen sink, many peaks exceeded 100 dBA.

For most events, five samples were taken and averaged. Care was taken to assure that the measuring equipment was not overloaded at any time. Considerable variation in observed levels is evident, not surprisingly in view of the uncontrolled nature of the activities. Table 1 separates the sounds according to whether they were measured at the 9-foot distance or at the kitchen sink location adjacent to the noise sources. As a side note, the item regarding the nail clippers is included because the author has wondered for a long time how such an insignificant activity could sound so loud. Here is the answer.

Kitchen sink area
(appr. 2 ft. distance)
Peak SPL (dB) Range (dB)
Close cupboard door 84 78-89
Set salt shaker on counter 87 84-94
Set lid on 6-inch pot 104 101-107
Set plate in sink 91 90-93
Put silverware in sink 87 83-93
Pots and pans in cupboard 89 88-94
Drop pot lid 3 inches to counter 102 100-105
Drop fork 1 inch to plate 104 101-107
Set soupspoon in bowl 103 98-107
Tap spoon on glass (attention) 97 94-101
Tap spoon on cup (attention) 104 102-105
Fingernail clippers in action 111 108-114
In breakfast nook
(9 ft. distance)
Dishes to cupboard 90 84-95
Close cupboard door 82 80-86
Set jar on counter 84 -
Drop teaspoon on tile floor 84 -
Put lid on frying pan 91 85-95

Are Those Noise Levels Bothersome?

The Environmental Protection Agency labels noises (dBs) in the mid-90s as “very annoying” and states that “100 dB can be produced by shouting in the ear.”5 Mean uncomfortable level (UCL) occurs in about 100-110 dB SPL, or HLs from normal up to 45 dB HL.6,7

In Fig. 1, which illustrates the sound of a dinner plate being placed on another plate, the highest peak extends to about 103 dB, and a broader peak of 30 mS duration at 101 dB before decaying. The entire sound last about 130 mS.

Figure 1

Fig. 1. Sound of a dinner plate on another plate.

The sound of the lid being placed on a 6-inch stainless steel pot (Fig. 2) peaks at 104 dB, with a ringing sound at 101 dB lasting about 25 mS. Setting a knife and fork on a plate (Fig. 3) hits an instant peak of 99 dB, and the sound exceeds 87 dB for about 200 mS.

Figure 2

Fig. 2. Lid placed on a 6-inch steel pot.

Figure 3

Fig 3. Set knife and fork on a plate.

Note that it is possible that such very short noises may not seem as loud to the listener as longer signals used for identifying UCL levels. The dB levels may therefore not be directly comparable. This phenomenon, called auditory integration, is well documented for threshold levels8; whether it holds at UCL levels is not clear. At threshold, greater signal levels are required for the same response when the signal is made shorter than about 200 mS, with an integration slope of 8-10 dB per decade. If the same integration slope is assumed for the sounds shown, then a reduction in perceived loudness of 8 dB applies to Figs. 1 and 2.

Why Do These Sounds Bug the User?

The anecdotal evidence of annoyance caused by kitchen-related sounds seems to be firmly associated with hearing instrument use. Why is that? While I am unaware of any controlled research in this area, one can speculate on the likely culprits.

It is not know whether the “noisy dishes irritant syndrome” affects linear and compression aids equally or not. The difference may arise because the two circuit types control their maximum possible output (MPO) differentially. The intensities of these sounds are high enough to momentarily drive nearly any hearing instrument to its saturated MPO. In compression aids, the momentary overshoot (“attack MPO”) is usually not, and thus may substantially exceed the UCL. In recent history, there have been compression aids on the market that had a separate peak-clipping adjustment for controlling the overshoot, but the author is not aware of any currently available at this time.

It is true that only a short portion (1-2 mS) of the ANSI attack time extends into the circuit’s MPO region but the peak of a pistol shot only lasts about 0.1 mS, and it sure is loud!. In linear aids, the MPO is theoretically controlled instantaneously, with no attack time. Thus, the problem of momentary excessive loudness should not arise. To repeat, we do not know whether that is true in practice. However, there is another factor common to both types of circuits: Amplifiers distort badly during the moments they are in saturated MPO, and the distortion may be contributing to annoyance. Again, this is an area that has not been explored to any great extent. There are tantalizing hints; there is research from the broader field of audio amplification that may or may not be applicable to hearing instruments, but not much concrete evidence.

Just one example: back in 1971, a paper from the Karolinska Institutet in Sweden9 investigated something they called forward distortion of hearing aids. This occurred during the recovery from momentary overload and caused serious intermodulation distortion. Sounds like the very thing that happens during dish clattering! No further work appears to have been done on this.

Acknowledgements

Many thanks to my wife, Margaret, for letting me record her meal-preparation activities. It got so she was apologizing for every unusual noise!

References

  1. Nerison A. Personal communication.
  2. Teder H, Noise and speech levels in noisy environments. Hear Instr 1990; 41(4):32-33.
About the author
Harry Teder

Harry Teder

Harry Teder was the chief engineer at Telex Hearing Aids starting from the 1960s until his retirement in the 1980s. Harry has been responsible for many innovations in our field such as the world's first wireless CROS hearng aid, as well as adaptive compression.