A Geiger counter is a device that is used to detect radiation.

We will be making a Geiger counter program.

As we all know, when radiation hits a computer program it removes exactly 1 byte at random. So a Geiger counter program is a program that itself does nothing, but when any byte is removed the modified program prints beep, to indicate the presence of radiation.

Answers will be scored in bytes with fewer bytes being better. Answers must be at least 1 byte.

Your program may print beep with trailing a newline or print a single newline for empty output, so long as it does so consistently. Your program may also use a different case for beep such as BEEP, bEEP, or Beep so long as it does so consistently.

Hexagony, 38 bytes

.....;p;<>b;e;/<b;e;;p...@@.......;@..

Try it online!

Verification program.

Lost, 303 293 263 253 238 bytes

v^^"peeb"</"beepvv"((>@@>>%%>>(((((([[[[[[[
>>>>>>>>>>//>>>>>>>>>>>>>>/>>/>>>>>>>>>>>>>>\
>>>>>>>>>//>>>>>>>>>>>>>>>/>>>>>>>>>>>>>>>>>>\
>//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\
>>>>>>>>>>>>>>>>>>>>>>>\>>>>>>>>>>>>>>>>>>>>>

Try it online!

Verification script (borrowed from user 202729's answer). Unfortunately this can only test half of the code at a time, but rest assured I've tested the whole program.

Ouch, this was a tough one. I'll quote WW's deleted answer:

Lost is perhaps the most interesting language for this challenge. In
Lost the start location and direction of the pointer is entirely
random, thus to make deterministic programs you must account for every
possible start location and direction. At the same time, by the nature
of this challenge you must also account for any single byte being
removed.

Unfortunately, his answer didn't take into account removing newlines, which screwed everything up.

Explanation:

(note that a few bytes might be off here and there)

First let's talk about the general structure of the code:

v^^"peeb"<</"beepvv"((>>>@@>>%%>>(((((([[[[[[[ Processing line
>>>>>>>>>>>//>>>>>>>>>>>>>>>>>>>/>>>>>>>>>>>>>>\ Beep line
>>>>>>>>>//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\ Back-up beep line
>//>>>>>>>>>>>>>>>>>>>>\>>>>>>>>>>>>>>>>>>>>>>>>\ Back-up return line
>>>>>>>>>>>>>>>>>>>>>>>>\>>>>>>>>>>>>>>>>>>>>>>> Return line

Everything but the processing line must be entirely composed of either > or one of /. Why? Well, as an example, let's remove a newline:

v^^"peeb"<</"beepvv"((>>>@@>>%%>>(((((([[[[[[[>>>>>>>>>>>//>>>>>>>>>>>>>>>>>>>/>>>>>>>>>>>>>>\
>>>>>>>>>//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\
>//>>>>>>>>>>>>>>>>>>>>\>>>>>>>>>>>>>>>>>>>>>>>>\
>>>>>>>>>>>>>>>>>>>>>>>>\>>>>>>>>>>>>>>>>>>>>>>>

The first line is now way longer than the rest of the block. If a pointer were to spawn on a non->/ character with vertical movement, then it would get stuck in an infinite loop.

The biggest radiation detector part is the section at the end of each line.

 
 \
 >\
 >>\
 >>>

Normally an IP passing through this from the first line would exit out the last line. However, if any character on the line is removed, then that line shifts down one, e.g:

 
 \
 >\
 >\
 >>>

And the IP instead exits out the line that is missing a byte (with the exception of the last line, where it exits out the second to last).

From there, each of the first four lines will redirect to the second line:

v
>>>>>>>>>>>
>>>>>>>>>//
>//

Which will then lead into either one of the two beepers.

v^^"peeb"<</"beepvv"((>
>>>>>>>>>>>//

If any of the bytes in the first beeper have been removed, then it instead goes to the second:

v^^"peb"<</"beepvv"((>
>>>>>>>>>>>//

Both beepers then lead back to the first line and the terminating @.

Some other miscellaneous parts:

The (((((([[[[[[[ is used to clear the stack when the pointer starts inside a pair of quotes and ends up pushing the whole first line to stack. It has to be so unfortunately long because the first newline can be removed to make the first line twice the size. Experimenting in generating the beep using arithmetic instead of quotes ended up longer.

The s and /s scattered across the lines are there to golf bytes in the top line of code by redirecting