High-frequency sounds tend to be more directional than lower frequencies due to a phenomenon called diffraction. Diffraction refers to the bending or spreading of sound waves as they encounter an obstacle or pass through an opening. The extent of diffraction depends on the wavelength of the sound wave in relation to the size of the obstacle or opening.
When a sound wave encounters an obstacle or passes through an opening, such as the human head or the outer ear, it diffracts or bends around the obstacle. The amount of diffraction increases with decreasing frequency and increasing wavelength. Lower-frequency sounds have longer wavelengths, so they tend to diffract more and wrap around obstacles more effectively.
On the other hand, high-frequency sounds have shorter wavelengths. As the wavelength decreases, the sound wave becomes less able to diffract around obstacles or openings, resulting in more direct propagation. This means that high-frequency sounds tend to travel in more focused paths and are less likely to deviate from their original direction.
This property is exploited in various applications, such as directional microphones or sound systems in which the design aims to enhance or suppress specific frequency ranges. By utilizing the directional properties of high-frequency sounds, it is possible to create focused audio pickup or targeted sound projection in specific directions.
It's important to note that while high-frequency sounds are generally more directional, the overall directionality of a sound wave can also be influenced by factors such as the size and shape of the sound source, the characteristics of the surrounding environment, and the presence of reflections or other acoustic phenomena.