Sound Diagnostics

Engine Sound Diagnostic Checklist

A step-by-step checklist for recording engine noises: vehicle details, the complaint, phone settings, the clips to record, where to place the phone, and the supporting data that sharpens the diagnosis.

1. Vehicle

Year, make, model
Engine size and engine code (if known)
Mileage
Fuel type (gasoline, diesel, hybrid)
Transmission type

2. Complaint

What the noise sounds like: knock, tick, rattle, squeal, whine, rumble, other
When it happens: cold start, warm idle, under load, coasting, turning, over bumps
How long it has been happening, and whether it's getting worse
Any related symptoms: misfire, loss of power, warning lights, stored codes

3. Engine state

Cold, warming up, or fully warm
Outside temperature
Warning lights on?
Stored codes (if available)

4. Phone setup

Noise suppression and automatic gain off, if the recorder allows it
44.1 or 48 kHz, high quality or uncompressed
Airplane mode on (stops radio interference in the audio)
Case removed if it covers the microphone
External microphone with a wind cover, if you have one
Bluetooth microphones and noise-cancelling apps off

5. Environment

Quiet space: no radio, compressors, or conversation
Out of the wind
Parking brake on, wheels chocked, transmission in Park or Neutral
Hood open

6. Clips to record

Record each as a separate clip, 15–30 seconds, and note the RPM for every clip.

Clip	How
Cold start	Start from cold; record the first 30 seconds
Warm idle	30 seconds at a steady idle
Slow sweep	Idle to about 2,500 RPM slowly, hold 5 s, back to idle
Snap throttle	Three quick snaps, not held
Steady RPM	1,500, 2,000 and 3,000 RPM, about 10 s each

7. Phone positions

Record the clip that best reproduces the noise from at least two positions, keeping everything else the same:

Front of engine (belt and timing-cover area)
Driver side
Passenger side
Top of engine (valve covers)
Tailpipe, for exhaust noises
Under the vehicle — only with the phone placed before the engine starts, and the vehicle on rated stands or ramps

8. Optional tests

Only when they relate to the complaint:

A/C on vs off
Steering at full lock (briefly)
Transmission in Drive, foot firmly on the brake
Electrical loads on (headlights, blower, rear defrost)
Cranking only, no start

9. Supporting data

Upload or paste anything you have:

Scan-tool live data: RPM, coolant and intake air temperature, fuel trims, misfire counters, MAF or MAP
Freeze-frame data and stored codes
Battery and charging voltage
Relative compression results
Scope captures from the same vehicle
Oil pressure readings (for knock complaints)

10. Service history

Last oil change, and the oil viscosity used
Plugs, coils, timing belt or chain: when last serviced
Recent repairs or collision damage

11. Before you submit

Each clip has its RPM and condition noted in the text field
No voices, music, or wind in the clips
The noise is audible in at least one clip
At least two phone positions recorded
Supporting data attached (if available)