Electronic sound when braking and when shifting into reverse/drive

Hi everyone, my 2009 Prius makes a sound similar to what I can best describe as an old computer struggling to complete a task when I either hit the brake or shift into drive or reverse. The sound is not constant, it happens when I begin moving always and when I slow down almost to a stop but never at speed. What could this be? Thank you.

Any dash lights light up when this happens? And dash warning lights on all the time? Check engine light? How many miles on this thing?

How long have you owned this Prius?
If you have owned it for a long time, is this noise a new phenomenon?

If you haven’t owned it for the long term, I am wondering if the noise that you hear when braking is the result of the car’s regenerative braking system being activated.

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The hydraulic brake pump is noisy. With the vehicle in park, apply the brake several times to see if you can replicate the noise.

Any other way you can describe the sound? I’m retired software engineer, been programming them since 1961, but I’ve never heard one “struggling to complete a task.” I’ve heard fan noise (hear it now on my desktop computer) and disk heads moving. I’ve also heard tape drives moving back and forth.

I miss the sound (and visual ) of 9 track tape drives on a 390.

Hi, I have 109,000 miles on this car. It only makes the noise occasionally. Has no codes shown and I seen a video making a similar sound to this and the video owner commenting saying it was the brake actuator. I’m wondering if that’s what I should be worried about though.

If the brake booster pump cycles on/off frequently without cause there may be a leak in the booster/accumulator assembly. To identify the source of the noise you will need to show someone what you are listening to.

There was a safety recall issued in 2013 to inspect/replace the brake booster pump assembly w/accumulator, if your vehicle has been to a dealer in the last 7 years this most likely has been completed.

There was a customer support program (warranty extension) to cover the brake booster pump assembly w/accumulator issued last year however it expires after 10 years from the date of first use or 150,000 miles.