Saturday, May 17

Quiet car observations

Greetings. I received the following email from a list. The original list that this was posted on was the Quiet Cars list. Incidentally, if you'd like to join this list, send a message to:

And put the word subscribe in the subject of the message. Leave the body blank and send, then just reply to the confirmation message, and you will be subscribed.

Hi Everyone-

It's Larry Rosenblum writing - the perceptual psychologist conducting
research on quiet car audibility. I thought that as you contact your
congressional representative, you might find the following
information useful. Pasted below is an op-ed piece I wrote that's
been published in a few newspapers. The piece makes the following
main points:

1) Research shows that the human brain is exceptionally sensitive to
approaching sound sources.
2) This brain sensitivity means that the audibility of moving
vehicles is an issue for everyone, blind and sighted alike.
3) This brain sensitivity means that only a very subtle enhancing
sound for quiet cars, at only low speeds, will be sufficient to fix
the problem. Loud beeps or chirps will not be necessary.

Hope this helps,

Larry R.

Don't worry: Hybrid cars won't beep, chirp, or make the world noisier

It's a noisy world, and getting noisier. This is likely why there has
been such strong reaction to a new congressional bill designed to
examine whether hybrid cars should be made more audible for
pedestrians, especially the blind. But as a scientist studying the
problem and advisor to the Society of Automotive Engineers, I bring
good news. We can have it both ways. Hybrid cars can stay quiet, and
still provide enough sound to be safe for us all.

The Pedestrian Safety Enhancement Act of 2008, introduced last month,
proposes a two year study determining the most practical way for
hybrid and electrical vehicles (EVs)-cars that are functionally
silent at slow speeds-to provide non-visual cues for pedestrians. The
solution will likely establish a minimal sound level for these cars.
The automotive industry will then have two years to incorporate this
change into new vehicles.

Sound noisy? Well it isn't, and here's why. First, hybrid and EVs are
functionally silent only when traveling in electric mode below 20
miles per hour. Faster than that, and all cars produce enough tire
and aerodynamic noise to be audible from a safe distance. Of course
it is at slow speeds that cars are closest to pedestrians, whether in
parking lots or backing out of driveways, and where the greatest
danger exists. But it is only at these slow speeds that some change
is necessary.

Secondly, only a subtle enhancement of sound will be needed. Hybrids
will not beep, or chirp, or produce an alarm. Beeps and chirps turn
out to be much more distracting than they are perceptually useful.
The enhancing sound, used only at slow speeds, will likely be either
the simulated sounds of a very quiet engine (think cooling fan), or
of rolling tires. For purposes of both auditory utility and simple
familiarity, the safest sounds are car sounds. And these sounds will
be barely noticeable for most of us. Not much sound is needed for the
auditory system to warn us about hazards, as long as it's the right

You have your brain to thank for this. The human brain is exceedingly
sensitive to approaching sounds. Research shows that when you hear a
sound approach-vs. recede or remain stationary-brain regions
associated with attention and motor action are quickly recruited. The
auditory brain also possesses a disproportionately large number of
cells sensitive to increasing sound loudness: one of the primary cues
for perceiving approaching sounds. Our brains have been designed to
use approaching sounds to avoid hazards. And this is true of
everyone's brains, blind and sighted alike.

This sensitivity of the brain likely means that we all use car sounds
to keep us safe, even if we are unaware of doing so. The auditory
system often works at an implicit level in warning of nearby dangers,
allowing us to concentrate on more conscious tasks. Your ability to
safely cross a parking lot while talking to a friend, manage your
children, or daydream, is facilitated by this implicit auditory
warning system. If there is too little sound to engage the system, as
is the case with hybrids at low speeds, then any normal distraction
becomes hazardous.

Thus, while the proposed bill was initiated by the needs of the
blind, a slight enhancement of quiet car sounds at low speeds will be
safer for us all. This will be even more true as the mean age of the
country increases, and more of us become sensory compromised. Perhaps
in ten years, we'll be thanking the blind community for making us all

While there are not yet definitive data showing that hybrids are
involved in more pedestrian accidents, these cars are still too new
for solid data to emerge. There are data however, suggesting that a
majority of the hybrid early adopters are particularly conscientious
drivers. But as hybrids and EVs become cheaper, and come in more
styles (a hybrid sports car appeared this year), a wider range of
drivers will be behind the hybrid wheel: a good reason to address the
problem preemptively. And needless to say, waiting for concrete
evidence of injury or death before addressing an obvious hazard is
not a sensible approach. This is especially true when the solution is
so simple and unobtrusive. Hybrids don't need to be made loud, they
just need to be made audible at slow speeds.

If you've not yet been surprised by the seemingly spontaneous
appearance of a moving hybrid in a parking lot or driveway, you will
be. Let's hope that when this happens, neither you or the driver are
talking to a friend, managing children, or daydreaming. Better yet,
let's hope you'll soon hear that hybrid make just enough quiet sound
so that you're not surprised at all.

Lawrence D. Rosenblum
Department of Psychology
University of California

1 comment:

  1. Hi Wayne:

    My name is Larry and I produce DisabilityNation, a program covering disability news and issues. I recently interviewed Lawrence Rosenblum for a program I did on quiet cars. The show also features Everett Meyer of Stanford University and is the second in a two part series examining the issue. The first program featured representatives from the National Federation of the Blind and the American Council of the Blind as well. I thought you and your readers might be interested. You can visit the DisabilityNation web site to learn more and to listen to these two programs.