21. At audio frequencies the impedance is far from constant and the nominal value is only correct at one frequency. 22. Using delta-sigma modulation, Super Audio CD obtains 120 dB SNR at audio frequencies using 1-bit audio with 64?oversampling. 23. Thus, valves with low noise at high frequency do not necessarily have low noise in the audio frequency range. 24. Consequently, practical ADCs at audio frequencies typically do not exhibit aliasing, aperture error, and are not limited by quantization error. 25. Some radio monitoring hobbyists record ELF pitch, so that it can be brought into the audio frequency range for audibility. 26. Each call sign is sent in Morse code generated at different audio frequencies and speeds, timed to overlap each other. 27. As the trail dissipates, megawatts of electromagnetic power could be released, with a peak in the power spectrum at audio frequencies . 28. This network and tower combination often results in a narrow bandwidth, severely limiting the audio frequency fidelity of the radio station. 29. An "'audio filter "'is a frequency dependent amplifier circuit, working in the audio frequency range, 0 Hz to beyond 20 kHz. 30. To make them audible, the tone wheel receiver used the heterodyne principle to convert the radio frequency to an audio frequency .
