What is a Resonator?

A resonator is a chamber in your exhaust that cancels particular sound frequencies, mainly the harsh rasp and the low boom (drone) you hear in the cabin at highway speed. It doesn't make the exhaust much quieter overall. It changes the tone, so the exhaust sounds clean rather than boomy.

How a resonator works

Exhaust noise is a mix of frequencies. Inside a resonator, sound waves bounce off the chamber walls and meet the incoming waves out of step, which cancels some of them out. The length and volume of the chamber decide which frequencies get cancelled, so a resonator is tuned for a sound result rather than being a one-size-fits-all part.

It usually sits in the mid-pipe, between the cat and the muffler, and looks like a short round or oval section that's wider than the pipe.

Resonator vs muffler

A muffler cuts overall volume. A resonator targets specific tones. Run a muffler alone and the exhaust can still drone at cruising revs. Run a resonator alone and the tone is smoother, but the volume stays loud. Most exhausts that sound good on a long drive use both, matched to each other.

Types of resonator

• Straight-through: a perforated tube wrapped in packing. It flows freely and keeps a sporty note while taking the edge off harshness. The packing wears over time, so the sound gets louder as it ages.
• Chambered: internal walls reflect the sound back on itself. Usually a deeper, mellower tone.
• Hotdog: a small straight-through body that fits where space is tight. See What is a Hotdog Muffler?

For example, the Redback Extreme Duty 5" round resonator muffler is a straight-through design built as part of the Redback Extreme Duty system.

Which suits your ute or 4x4?

If your turbo-diesel ute drones on the highway, a resonator matched to your muffler is usually the fix, rather than a louder system. If you want more character, a straight-through resonator with a performance muffler gives a sportier note that's still liveable on long trips. Either way, choose the resonator and muffler together.

What is a resonator delete?

A resonator delete replaces the resonator with a straight piece of pipe. The exhaust gets louder and the tones the resonator was cancelling come back, which on many four-cylinder diesels means drone at highway cruise. On a road vehicle, swapping to a better-matched resonator usually gives a better result than deleting it. Noise rules for road-registered vehicles are set by each state, so check yours before modifying.

Signs your resonator is failing

• The exhaust sounds louder, harsher or more droney than it used to
• Rattling underneath, often a broken baffle or loose bracket
• Rust, cracks or holes in the body
• Exhaust smell in the cabin. Get this checked straight away.

Rattles can also come from heat shields and hangers, so check those at the same time.

Finding the right resonator

Measure your pipe diameter and the space available before you buy. Browse Mufflers & Resonators or Bolt In Mufflers, Hotdogs & Muffler Delete Pipes, and hear how different setups sound in our Exhaust Sounds Hub. Replacing the whole system? Use Find Your Vehicle at the top of the page. Not sure what you need? Get in touch and our team will help.