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A frequency response diagram plots the microphone sensitivity in decibels over a range of frequencies (typically 20 Hz to 20 kHz), generally for perfectly on-axis sound (sound arriving at 0° to the capsule). Frequency response may be less informatively stated textually like so: "30 Hz–16 kHz ±3 dB".
The frequency response is characterized by the magnitude, typically in decibels (dB) or as a generic amplitude of the dependent variable, and the phase, in radians or degrees, measured against frequency, in radian/s, Hertz (Hz) or as a fraction of the sampling frequency.
The typical resonant frequency of those microphones is within the range of human hearing. So even the very early commercially available ribbon microphones had excellent frequency response throughout the nominal range of human hearing (20 Hz to 20 kHz for a young adult).
The frequency response of most carbon microphones, however, is limited to a narrow range, and the device produces significant electrical noise. Before the proliferation of vacuum tube amplifiers in the 1920s, carbon microphones were the only practical means of obtaining high-level audio signals.
Frequency response 50 to 15,000 Hz Polar pattern Cardioid, rotationally symmetrical about microphone axis, uniform with frequency Sensitivity (at 1,000 Hz Open Circuit Voltage) −54.5 dBV/Pa (1.85 mV); 1 Pa = 94 dB SPL Impedance Rated impedance is 150 Ω (300 Ω actual) for connection to microphone inputs rated low impedance Polarity
The frequency of the resulting howl is determined by resonance frequencies in the microphone, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the microphone and loudspeaker, and the distance between them.
Two examples of different boundary mics (top) and a diagram of the elements of a boundary microphone. The diagram shows the location of the mic capsule, the plate, the aperture, and the pressure zone.
The microphone's proximity effect is adjusted so that flat frequency response is achieved for sound sources very close to the front of the mic – typically 1 to 3 cm. Sounds arriving from other angles are subject to steep midrange and bass rolloff.
Response and output characteristics. At 1 kHz, the 77-DX has an output of -50 to -56dbm, depending on the pattern selection. The output impedance is user-selectable; factory preset at 250 ohms, and changeable to 30 or 150 ohms. The microphone has a fairly flat response.
The proximity effect in audio is an increase in bass or low frequency response when a sound source is close to a directional or cardioid microphone. [1] [2] Proximity effect is a change in the frequency response of a directional pattern microphone that results in an emphasis on lower frequencies.