. . .
And, in a moment of (drunken?) lunacy, I found a much simpler way of testing the mufflers than using a dyno and the rest of the gear. In short, I simply grabbed a muffler and yelled through it. And then another muffler, and then another muffler…

Using a sound pressure level meter, I found that at a distance of about 2 metres, my prolonged unmuffled yell recorded a consistent 100 dB(A).
Through one muffler the yell was subdued to 76 dB(A), another recorded 80 dB(A), another was at 82 dB(A) and one didn’t drop the level at all - ie it stayed at 100 dB(A).

The fascinating thing is that the order and relative magnitude of these figures closely matched the results I achieved at full load on the test car!
. . .
The Jaguar mufflers (resonators, really) are compact, straight-through designs. They’re off a supercharged XJR100.

The ‘yell’ test indicated that the Ferrari mufflers were nothing special. With the variable valve open, they barely subdued the yell, and even with it shut, the yell was still pretty loud. But the little Jaguar resonators were something else. Simply, they’re stunningly effective.

They seemed so good that I reached for the noise meter.

This time (different noise meter and about 13 years later!), my naked yell recorded 92 dB(A). Through the Jaguar muffler this dropped to 73 dB(A). That attenuation is 19 dB, versus a best in the previous ‘test’ of 24dB. But the previous results were with large body, 3 inch mufflers! The Jaguar mufflers have vastly less volume (and it must be said, at 1.75 inches, smaller diameter tube as well).

But an even better result was achieved with my wife, Georgina, as the yeller. As you might expect, her yell [92 dB(A)] was higher pitched. And, as theory suggests should be the case, the straight-through muffler worked even better with the higher frequencies. The reduction in noise level was an amazing 27dB!

A reduction of this magnitude is a decrease in sound power of 99.8 per cent.
. . .