Consider an audio speaker system with filter circuits. These circuits selectively pass desired frequencies while attenuating others, limiting signals to a specific frequency band.

Filters are categorized as passive when exclusively using passive components like resistors, inductors, and capacitors.

A low-pass audio filter channels low-frequency components to the woofer or subwoofer, while a high-pass filter directs high-frequency components to the tweeter.

The transfer function, expressed as the output-to-input voltage ratio, is estimated for low and high frequencies to achieve the desired frequency response for the filter circuits.

Well-designed filters transmit frequencies up to the cutoff frequency without attenuation for low-pass filters, and above the cutoff frequency for high-pass filters.

A band-pass filter directs mid-range frequencies to the dedicated driver. While, a band-stop filter targets overlapping frequencies to prevent interference.

Similarly, the transfer function can be approximated for low and high frequencies to optimize the frequency response of band-pass and band-stop filters.

Band-pass filters transmit frequencies around a center frequency, whereas band-stop filters block these frequencies.