Why can adding turbochargers make a sports-car exhaust note feel less raw?

Answer: Turbines eat exhaust energy

Boost adds raw exhaust — Not quite. More boost can help make more power, so it feels natural to expect a more brutal exhaust. But a turbocharger gets that boost by putting a turbine in the exhaust stream and harvesting exhaust energy. Some energy that might have gone straight to the tailpipe is doing work first. The twist is that the power-making part can also take away some rawness.

Turbines eat exhaust energy ✓ — Right. A turbocharger's turbine sits in the exhaust stream and extracts energy to drive the compressor. That makes power and efficiency possible, but it also means less raw exhaust energy is left to travel straight to the outlet. Some road tests of modern turbo performance cars describe the result as muted or muffled compared with earlier or more naturally exposed engines. The counterintuitive bit is that more power hardware can remove some acoustic rawness.

Turbo sits off exhaust path — Not quite. A turbocharger is easy to imagine as only an intake booster because it compresses air going into the engine. But the compressor is driven by a turbine placed in the exhaust stream. That means exhaust energy is being tapped before the tailpipe can turn it into raw sound. The acoustic change begins in the exhaust path, not outside it.