Press the pedal (higher = more throttle) or hold Space. The engine revs freely in neutral.
What you hear is mostly the exhaust: a burst of hot gas each time an exhaust valve opens. The firing frequency is rpm ÷ 60 × cylinders ÷ 2, so an inline-4 at 3,000 rpm pulses 100 times a second and a V8 200 times.
Timing matters as much as count. A cross-plane V8 fires evenly overall, but each bank fires at 90-180-270-180° gaps, and that unevenness reaching each pipe is the burble. A flat-plane V8 alternates banks, so each pipe sees even pulses and it screams like two inline-4s.
The crank angle advances sample by sample. At each cylinder's firing angle a pressure pulse is made, shaped by rpm, load and cylinder size, and delayed by that cylinder's header length. Pulses run through the collector, a turbine if fitted, a muffler chamber and a tailpipe modelled as a delay line whose open end reflects the wave back.
Intake pulses ring the airbox, valves click, a turbo whistles and vents through its blow-off valve, a blower whines at its lobe frequency. A small physics model handles inertia, idle control, the rev limiter, fuel cut on the overrun and gear changes.