Speeds of 50–70 MPH in a convertible car generate noise levels above the threshold of hearing damage, according to a study published in the medical journal Otolaryngology – Head and Neck Surgery.
Researchers Philip Michael and Michael C.F. Smith measured noise levels with an iPhone running DbMeter Pro at speeds of 50, 60 and 70 MPH in various convertible cars on both sides of the driver’s head.
Their measurements indicate little difference in noise levels relative to speed: 86, 86 and 87 decibels were measured for the three speeds, respectively, with a peak of 97.
Michael and Smith conclude that “noise experienced arises due to a combination of factors including road surface, traffic congestion, and type, as well as speed and car type. However, while motorcyclists are well versed in using ear protection, this study highlights that drivers of convertible automobiles may also be at risk of noise-induced hearing loss.”
Eighty-five decibels is the threshold above which hearing loss becomes a risk—and the measured peak of 97 is enough to cause hearing damage after 15 minutes of unprotected exposure. The researchers have found that rolling up the windows cuts noise to below that threshold. This, however, can interfere with cocking your elbow out the window, so it might not be a viable suggestion for convertible owners.
Decibel is a logarithmic unit, meaning a numerical increase of 10
corresponds to a doubling of sound amplitude
doubles the subjective loudness of the sound. Here’s some common sounds to put these numbers in perspective:
- 80 dB: average city traffic, garbage disposal
- 84 dB: diesel truck (at 40 MPH from 50 feet)
- 85–90 dB: lawnmower, food blender
- 88 dB: subway, motorcycle from 25 feet
- 98 dB: farm tractor
Just the thing to read on an Indian summer day. You can hear a thousand Miatas weeping.
Source: Otolaryngology – Head and Neck Surgery (research), National Institute on Deafness and Other Communication Disorders (noise level comparisons)