In a noisy environment, you definitely won't be able to hear them, but if you're in a place where you can turn off lights, radios, televisions and other sources of sound, you may be able to hear a camera activate.
Unfortunately, the above methods aren’t foolproof — but don’t give up just yet.
Go slowly, and examine suspicious places from multiple angles.
This method still isn't perfect, as you'll need to shine the light from the right angle and, with some devices, be fairly close to the camera to spot it.
The most straightforward way to find a hidden lens using a light source is to turn off the lights and pan a flashlight around the room.
These apps use your smartphone's flash to light up camera lenses and help you detect them, though many have received negative reviews, which speaks to how tough it can be to spot a hidden camera.
For i Phone, there's Spy Hidden Camera Detector ($2.99); for Android, try Glint Finder (free, with advertisements).
Just this year, a Chipoltle employee in Texas was accused of planting a hidden camera in the women's bathroom.
In California, a Comfort Inn employee was arrested for installing a light bulb with a built-in camera above the toilet in one of the guest rooms — and these tiny, inconspicuous cameras can be easily bought online.
These cameras have plenty of perfectly legitimate uses.
They can provide security in public spaces and prevent theft in businesses.
If you're reading this article on your phone while waiting for your morning coffee, there's probably a camera keeping an eye on you right now.