T-Sport: Keeping the Peace

How Loud is LOUD?

Before the Screamin' Eagle slip-ons would be swapped out, I wanted to record the sound levels they actually produced. I had purchased an analog decibel meter from Radio Shack a couple of years earlier for balancing my home theatre sound system, but had never gotten around to doing so. Dusting it off, I was happy to find that the batteries still carried some juice. I mounted the meter to a camera tripod and took it out to the driveway. Measuring twenty feet from the tip of the muffler, I positioned the equipment behind the bike and appointed my daughter as the official meter reader. After several minutes of engine warm up, we were ready to rock.

The readings I got were as follows:

1,100 rpm = 76-77 dB
2,000 rpm = 82 dB
3,000 rpm = 89.5 dB
4,000 rpm = 97 dB

To put some meaning to these figures, I did a search on the internet to obtain the sound levels of typical noise sources. I found a table doing just that here. The following is an extraction of some of the data from the 1970 publication:

00 dB - Threshold of hearing
40 dB - Lowest limit of urban ambient sound
60 dB - Conversation
64 dB - Electric typewriter at 10 ft.
80 dB - High urban ambient sound
84 dB - Diesel truck 40 mph at 50 ft.
88 dB - Propeller plane flyover at 1000 ft.
89 dB - Car wash at 20 ft.
92 dB - Jackhammer
96 dB - Lawnmower
103 dB - Jet flyover at 1000 ft.
108/114 dB - Rock Band

Keep in mind that the subjective loudness (relative to 70 dB) is twice as loud at 80/89 dB, four times as loud at 90/99 dB, 8 times as loud (or very loud) at 100/109 dB, 16 times as loud at 110/119 dB, and finally, at 120 dB plus it becomes uncomfortably loud, or 32 times as loud.

Based on this information, I now had confirmation that my bike was indeed loud and that my friends were not exaggerating when pointing this out to me.