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???
06/21/06 07:15
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#118693 - Adding signals with two frequencies
Responding to: ???'s previous message
Then, when a cell phone produces the 17 kHz tone would there not be a beat frequency (hetrodyne if my spelling is correct) of the difference?<p>

No. Adding two signals that contain two different frequencies will result in a signal that contains both frequencies, and just that. Without further processing, no additional frequencies will appear.

However, the sum signal could be rectified (AM demodulation), which would result in an audible frequency. That would require recording the sum signal, which makes the whole process pretty much useless, because it requires a speaker and a microphone. Detecting high-pitches tones directly could be done with a microphone only.

List of 23 messages in thread
TopicAuthorDate
High pitched ring tones            01/01/70 00:00      
   LM556            01/01/70 00:00      
   Download The Ring Tone.            01/01/70 00:00      
   Adding signals with two frequencies            01/01/70 00:00      
      Sure?            01/01/70 00:00      
         Yes, quite sure.            01/01/70 00:00      
            Intermodulation not beat frequencies            01/01/70 00:00      
               Remember piano tuners            01/01/70 00:00      
                  A test should tell it            01/01/70 00:00      
                     Tuning instruments.            01/01/70 00:00      
                        Yes, but...            01/01/70 00:00      
                           Mixing 2 ultrasonic frequencys            01/01/70 00:00      
                              Cool!            01/01/70 00:00      
                                 We experimented with the "ionovac"            01/01/70 00:00      
                              Mixing two rf signals            01/01/70 00:00      
   Adding signals with two frequencies            01/01/70 00:00      
   Don't do that!            01/01/70 00:00      
      I'm with Andy            01/01/70 00:00      
         active noise reduction            01/01/70 00:00      
         Rest your fears            01/01/70 00:00      
   a better idea            01/01/70 00:00      
   Detecting high pitch sounds            01/01/70 00:00      
      No, no, do it the hard way            01/01/70 00:00      

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