When you hear sound from behind a loudspeaker, it’s because sound waves propagate in all directions from the speaker. Sound is a longitudinal wave that travels through air or other mediums by compressing and decompressing the molecules. When the speaker emits sound, it generates these waves uniformly in all directions. If you are positioned behind the speaker, you can still hear the sound because the waves spread out in a spherical pattern. This means that even though the speaker is facing forward, sound waves propagate around it and reach your ears from the rear.
You can hear sound from a loudspeaker due to the vibration of its diaphragm. Inside the loudspeaker, an electrical signal is converted into mechanical vibrations by the diaphragm, which moves back and forth rapidly. These vibrations create changes in air pressure, producing sound waves that travel through the air to your ears. Your ears detect these pressure fluctuations and convert them into electrical signals that your brain interprets as sound.
Sound is heard from a speaker through the process of transduction. As electrical signals from an audio source pass through the speaker, they cause the speaker’s components (such as the diaphragm and voice coil) to vibrate. These vibrations generate compressions and rarefactions in the air, creating sound waves that propagate outward. When these waves reach your ears, your eardrums vibrate in response to the changes in air pressure, and this mechanical energy is converted into nerve impulses that your brain interprets as sound.
The ability to discern where a sound is coming from is primarily due to two factors: intensity and timing differences between the sound arriving at each ear. Intensity differences occur because the head creates a sound shadow, attenuating the sound reaching the far ear. Timing differences arise because sound travels slightly faster to the ear closer to the sound source. These subtle cues are processed by the brain to localize the sound’s origin, providing spatial awareness of the sound’s direction.
The physics behind speakers involves the conversion of electrical signals into mechanical vibrations and subsequently into sound waves. Inside a speaker, an electrical audio signal drives a coil of wire (voice coil) attached to a diaphragm. When the electrical current flows through the voice coil, it interacts with a magnetic field created by a permanent magnet, causing the coil and diaphragm to move rapidly back and forth. This movement creates changes in air pressure that correspond to the original audio signal, generating sound waves. The size and shape of the speaker components, along with the properties of the materials used, influence the quality and characteristics of the sound produced.