An air carrier captain reports a loud bong sound on frequency 124 pt 35 while on the north downwind ...

Attributes
ACN	339981
Time
Date	199606
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : san
State Reference	CA
Altitude	msl bound lower : 5000 msl bound upper : 10000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : san
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 12000 flight time type : 1500
ASRS Report	339981
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other other
Consequence	Other
Supplementary
Air Traffic Incident	other
Situations
ATC Facility	other physical facility

Narrative:

Socal approach control frequency 124.35 has a loud buzz intermittently when nobody is transmitting on the frequency. It is very annoying. Callback conversation with reporter revealed the following information: the noise sounded like a 'bong' about every 10 seconds on the frequency, and continued until the reporter was handed off to another frequency. When the reporter told the controller that he was hearing the noise, the controller told him that they had received other complaints, too. Reporter states that he has heard this sound before so he knows that it wasn't related to this aircraft's radios. The sound caused the most interference between 5-10 mi northeast of the airport, on the downwind to runway 27, and while the aircraft was descending from 10000 ft to 5000 ft. This air carrier B737 captain also believes that the noise may be related to the nearby military facility (north island NAS) radar and other installations.

Original NASA ASRS Text

Title: AN ACR CAPT RPTS A LOUD BONG SOUND ON FREQ 124 PT 35 WHILE ON THE N DOWNWIND FOR RWY 27 AT SAN.

Narrative: SOCAL APCH CTL FREQ 124.35 HAS A LOUD BUZZ INTERMITTENTLY WHEN NOBODY IS XMITTING ON THE FREQ. IT IS VERY ANNOYING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE NOISE SOUNDED LIKE A 'BONG' ABOUT EVERY 10 SECONDS ON THE FREQ, AND CONTINUED UNTIL THE RPTR WAS HANDED OFF TO ANOTHER FREQ. WHEN THE RPTR TOLD THE CTLR THAT HE WAS HEARING THE NOISE, THE CTLR TOLD HIM THAT THEY HAD RECEIVED OTHER COMPLAINTS, TOO. RPTR STATES THAT HE HAS HEARD THIS SOUND BEFORE SO HE KNOWS THAT IT WASN'T RELATED TO THIS ACFT'S RADIOS. THE SOUND CAUSED THE MOST INTERFERENCE BTWN 5-10 MI NE OF THE ARPT, ON THE DOWNWIND TO RWY 27, AND WHILE THE ACFT WAS DSNDING FROM 10000 FT TO 5000 FT. THIS ACR B737 CAPT ALSO BELIEVES THAT THE NOISE MAY BE RELATED TO THE NEARBY MIL FACILITY (NORTH ISLAND NAS) RADAR AND OTHER INSTALLATIONS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

An air carrier captain reports a loud bong sound on frequency 124 pt 35 while on the north downwind for runway 27 at san.