Sony SRP-X500P System Integration Manual

Also see for SRP-X700P: User manual Interface manual Operating instructions Brochure Operating instructions

256 AppendixFeedbackWhat is feedback (howling)?Feedback in a sound system incorporating microphones andspeakers is the ringing or screeching noise you occasionallyhear. This phenomenon is often called “howling.”Mechanism of howlingIn a sound system, the microphone signal is amplified andoutput from a loudspeaker. However, the output signal issometimes picked up by the microphone again, and loopsaround the microphone, amplifier, and speaker. If the loopgain reaches one time or more, the signal is limitlesslyamplified. This is when howling occurs.Frequency response between microphones andspeakersControlling the frequency response between microphonesand speakers is the key to suppressing howling. Theresponse varies depending on the width of the room, thematerials of the wall and ceiling, and the speaker location.Feedback reductionThe feedback reduction incorporated in the SRP-X500Pscans the audio spectrum each time the button is helddown (for two seconds or more) to detect the howlingfrequency points and suppress the level of the detectedfrequency bands. This process is performed independentlyfor each microphone input. If you change the type orlocation of a microphone, feedback reduction should beactivated again in order to optimize the amount offeedback reduction.Automatic Gain Control (AGC)Varying audio volumeWhen picking up sound with microphones, the volumediffers from person to person, and depending on thedistance between people’s mouths and the microphone.The Automatic Gain Control (AGC) function closes thesegaps and maintains a constant audio level. AGC consists ofthree processes - compressor, make gain, and gate.CompressorCompressor is used to suppress loud sounds. COMPTHRESHOLD and RATIO can be adjusted.Make gainMake gain boosts the volume of a small voice to maintainthe total volume at a constant level.GateWhile make gain amplifies the signal level, ambient noisemust be controlled when the presenter is silent. Gatesuppresses ambient noise, with an ability to adjust theGATE THRESHOLD and RANGE.Loop-GainLoop-Gain1.01.0Howling occursFrequencyFrequencyAttenuate the howling pointMechanism of HowlingOutput levelCOMP THRESHOLDOutput levelOutput levelGATE THRESHOLDRATIOClosethe gapTimeTimeTimeMAKE GAINRANGERRATIOMAKE GAINRANGECOMPTHRESHOLDMAKE GAINGATETHRESHOLDCompressorMake GainGate