Mechanical filters are devices that selectively allow certain frequencies of sound or vibrations to pass through while blocking others. They are commonly used in various applications, such as audio equipment and vibration isolation systems, to improve performance by reducing unwanted noise or interference. These filters work based on physical properties, such as mass and stiffness, which determine their response to different frequencies. For example, a spring can be used to create a low-pass filter, allowing low frequencies to pass while attenuating higher frequencies. This makes mechanical filters essential in fields like acoustics and engineering.