Lack of experience with silencing in pre war times meant they were not particularly effective, the slanted rectangle design consisted of a large open chamber with partitioned entry and exit pipes. However, the recognisable sound given off by a Brooklands can meant it was adopted by many racers and owners for cosmetic purposes and to obtain the fashionable Brooklands rattle. Nowadays the iconic appearance of the Brooklands can is a fitting addition to many road and race vintage motorcycles built around the time of the banked circuit's heyday.
Both cars and motorcycles used the fishtail Brooklands can, some with cheese holed fins to lessen the amount of power robbing back pressure.
Source: Real Classic
Source: 'Copperknob' from The National Motorcycle Museum
Just imagine the sound of a whole field of pre-war racing cars or motorcycles roaring around the old banking all blurting through their fishtail Brooklands cans...