¶ Whistle
Description:
Whistle glitches (also known as Radio Frequency Beat Notes) usually appear in time-frequency plots with a characteristic 'W' or 'V' shape that start at higher frequencies.
Whistles are caused by radio frequency signals (i.e. signals at MHz frequencies) that beat with the LIGO Voltage Controlled Oscillators (VCOs). When the VCO and radio frequency signals are close enough in frequency, the frequency of the resulting beat note, f_beat = |f_VCO - f_RF|, will enter into the LIGO frequency band. Because the VCOs usually have rapidly changing frequencies, f_beat can change quickly, sometimes thousands of Hz in just a second or two.
Whistles occur at both LIGO-Hanford and LIGO-Livingston and contaminate searches for binary black hole mergers.
Cause:
Radio frequency signals that beat with LIGO Voltage Controlled Oscillators.
Status:
Active.
Examples:
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Audio Example:
Make sure to wear good headphones!
More Information:
- See this paper for more information about whistle glitches.