# Doppler Trainer — Sonar operator ear training

> Sonar operator ear training (iPhone/iPad app by Marc Ennis.)

- Source: https://appshunter.io/ios/app/doppler-trainer/id6810904553 (this page in markdown: same URL + `.md`)
- Developer: [Marc Ennis](https://appshunter.io/developer/6810904555)
- Category: Education, Games, Simulation
- Price: Free
- Age rating: 4+
- Requires: iOS 17.0 · 3 MB
- Languages: American English
- Released: 2026-10-07
- Data updated: 2026-10-10

## What is Doppler Trainer?

Doppler Trainer puts you at a sonar operator's console. Learn to hear what a contact is doing, understand why it sounds that way, and put a submarine on the plot.

EAR TRAINING
Listen to a contact and call its motion: Closing, CPA, or Opening. A closing contact sounds above its true frequency, an opening contact sounds below it, and at the closest point of approach you hear the true tone. Watch the signal on a waterfall or spectrum display and track your score.

DOPPLER LAB
Choose a frequency, a motion, and a speed in knots, then play the tone. See the source and observed frequencies side by side and hear how higher speed or higher frequency pulls the tone farther from true, while CPA stays on it at any speed.

dB LAB
Work an acoustic budget. Set source level, ambient noise, receiver sensitivity, and frequency, then drag the range. Transmission loss from spreading and absorption grows with distance until the signal goes from CLEAR to MARGIN to MASKED. Load presets from submarine tonals and blade rate to rain, surf, and shipping noise.

TACTICAL FIX
Three sonobuoys. One submarine. Choose LOFAR buoys, which report frequency and relative amplitude (louder is closer, no bearing), or DIFAR buoys, which add a bearing to the contact. Listen to each buoy, read its Doppler, place your fix on the overhead tactical plot, set the contact's heading on the compass, and submit. The debrief shows your position and heading error. Enter a callsign to rank your best rounds.

BUILT FOR LEARNING
• On-screen coaching walks new operators through each mode
• All audio is synthesized on the device; headphones help with low frequencies
• Works offline. No account, no ads, no data collection

Doppler Trainer is an educational simulation. It is not affiliated with or endorsed by any navy or government agency.


## Version history (last 1 release)

### 1.0 — 2026-10-08

No release notes.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-10.*