Odd happened. In the past week or so that I have had the machine I have tested it many times to become familiar with target id and sounds. Well today I noise canceled and I heard the threshold hum loud and clear during the noise cancel. This is the first time I had this happen. OK iturned the machine off. Removed the battery. Turned it back on and same thing loud and clear threshold during noise cancel. Any thoughts on why my trac is doing this or how to fix it would be great. Thank you HH c t