An ear on the traffic

Who hears more of the traffic buzz – a driver using his in-car music system or a bike rider using an iPod and earphones? Simon Vincett and Stephen Huntley went seeking evidence.

A month ago we posted this video we made before our test.

Now we can bring you the conclusions.

On a busy arterial road, cars and trucks surge past in jostling packs. The occasional coach and tram add to the din and motorbikes screech through gaps. Bike riders belt along the bike lane. The waves of noise ebb and flow. This is the urban soundscape.

We visited this busy road to test how much of this soundscape is deadened by wearing earphones while you ride, and as an interesting counter measure, how it compares to car drivers using their music systems.

On our test street (St Kilda Road, Melbourne) the waves of noise averaged 80 decibels (dB) at their loudest. Our test car (Nissan X-Trail 2005) was parked on the same street.

We were equipped with a decibel meter and a synthetic model ear specifically created for us by our regular collaborator at RMIT Industrial Design, Dr Scott Mayson. The ear was designed to fit the decibel meter in the back and earphones in the front.

It was immediately obvious that the type of earphones used make a big difference to what is heard. The ear-bud type that come with an iPod, and that sits in the outside of the ear canal, let in more outside noise than the in-ear type that plugs into the ear canal.

With the ear-bud in our synthetic ear but not playing music, we measured the ambient traffic noise at 79dB. With the in-ear earphones, the traffic noise was 71dB.

We also quickly established that cars are remarkably soundproof. We measured the average peak of ambient traffic noise inside the car (with the motor running) to be 54dB, which is 26dB quieter than outside the car. We rang a bike bell right outside an open car window and measured it from in the car at 105dB. With the window closed, the same bell registered just 57dB.

Using our own taste as a guide, we established that a reasonable volume for listening to music through our earphones while riding at our location was three clicks down from the maximum volume of our iPod, which turned out to be 87dB; greater than the average peak of the ambient noise.

We then set up with testers 10 metres apart. One called out “Passing”, then rang a bike bell, and neither registered on the decibel meter above the ambient noise. Despite this, when a tester put the ear-bud earphones in and played music at 87dB, they could clearly hear their fellow tester’s call out, and the ringing of the bike bell.

The call and bell could also be heard with the in-ear earphones, but only faintly.

What was startling, however, was what could be heard from the car with its stereo on at what was perceived as a moderate level; (69dB). Our driver was unable to hear our tester, stationed 10 metres away, calling out “Passing”, or the bike bell. Without the car stereo on it was just possible to hear the call and bell; it registered at a similar level to having the in-ear headphones in.

Conclusions

Based on these relatively simple tests, it is fair to conclude that:

A bike rider with ear-bud earphones playing music at a reasonable volume hears much more outside noise than a car driver, even when that driver has no music playing. A bike rider with in-ear earphones playing music at a reasonable volume hears about the same outside noise as a car driver with no music playing, but more than a car driver playing music. Ear-bud earphones set at a reasonable volume still allow riders to clearly hear the warning sounds of other riders.

The set-up

Test location: St Kilda Road, Melbourne

Time: Thursday 2–4pm

Car: Nissan X-Trail 2005

Music: “Lust for life” Iggy Pop

All measurements were made in dBA.

A bit about decibels

Decibels are measured on a logarithmic scale and can’t be simply added and subtracted. Here’s a guide to the decibels of familiar sounds:

0dBA the softest sound you can hear

20dBA a whisper

50dBA rainfall

60dBA ordinary speaking

90dBA a lawn mower

110dBA a rock concert

From www.dangerousdecibels.org

Here’s an interview about this article with the ABC radio program, The Sunday Spin

Music for surgery

Ninety per cent of surgeons in the UK perform operations to music, The Guardian reported in September 2011. An earlier study found that listening to self-selected music leads to decreased stress and increased performance for experienced surgeons who like to listen to music while operating. However, novice surgeons performed less well when listening to music.

For a review of headphones for running see Gizmodo

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