When you put your hands around your ears, forming a cup shape, you may hear a hissing sound. This phenomenon is known as the "hand cupping effect" or "hand occlusion effect." It occurs due to the way sound waves interact with your hands and the external auditory canal.
Here's how the hand cupping effect works:
Sound Reflection: When you cup your hands around your ears, you create a concave shape that acts as a reflector for sound waves. Sound waves from the environment enter this enclosed space created by your hands.
Amplification and Resonance: The concave shape of your hands focuses and directs the sound waves toward your ears. This amplifies certain frequencies within the sound spectrum, particularly those that match the resonant frequencies of the cupped space.
Feedback Loop: The amplified sound waves can travel back out of the cupped space and re-enter your ears. This creates a feedback loop where the sound waves are repeatedly amplified and reinforced.
Hissing Sound: As the amplified sound waves bounce back and forth between your hands and ears, they can create interference patterns and generate a hissing or shushing sound. This sound is a result of the specific resonant frequencies and the constructive and destructive interference occurring within the cupped space.
It's worth noting that the exact sound produced can vary between individuals and is influenced by factors such as the shape of your hands, the size of the cupped space, and the specific frequencies present in the surrounding environment.
The hand cupping effect demonstrates how our perception of sound can be influenced by modifying the acoustic environment around our ears.