Protection against sound piracy by microphones
Aspects of this invention include devices and methods for protecting acoustic signals from being pirated by a microphone. Such devices include a signal generator adapted to produce acoustic signals (“aliasing signals”) having frequencies greater than about ½ of the sampling frequency of the microphone Methods for protecting against piracy include providing an acoustical signal within the range of frequencies of normal human hearing to be protected, and a second signal having frequencies above about ½ the sampling frequency of the microphone. Additional aspects include amplifiers for aliasing frequencies and housings for both acoustical signal and aliasing signals.
1 . A method for protecting against microphone audio piracy, comprising:
(a) providing a first audio signal to be protected, having a range of audio frequencies within the range of human hearing;
(b) providing a second acoustical signal having a second frequency above the range of human hearing, wherein the frequency above the range of human hearing is greater than about ½ of the sampling rate of said microphone.
2 . The method of claim 1 , wherein said range of frequencies in step (a) has:
a lower limit of: about 20 Hz; and
an upper limit of about 20 kHz.
3 . The method of claim 1 , wherein the second frequency is above about 20 kHz.
4 . The method of claim 1 , wherein said steps (a) and (b), when captured by said microphone, produce an aliasing signal.
5 . The method of claim 1 , wherein in step (b) said second frequency is randomly varied.
6 . The method of claim 1 , wherein said second frequency has a sinusoidal wave form.
7 . The method of claim 1 , wherein said second frequency has a waveform having a sharp corner.
8 . The method of claim 7 , wherein said waveform is a square wave.
9 . A device for protecting against microphone audio piracy, comprising:
a signal generator adapted to produce a signal having a frequency above the range of human hearing;
an air transducer; and
a speaker for producing an audio signal to be protected.
10 . The device of claim 9 , wherein said device and said speaker are within a housing.
11 . The device of claim 8 , wherein said signal generator is adapted to produce a signal greater than about 20 kHz.
12 . The device of claim 8 , wherein said signal generator is adapted to produce a randomly varying frequency.
13 . The device of claim 8 , wherein said signal generator is adapted to produce a wave form having a corner.
14 . The device of claim 13 , wherein said waveform is a square wave.
15 . A method for protecting against music piracy, comprising:
(a) providing a music file containing a signal having a frequency above that of the range of human hearing; and
(b) providing a music player having a filter to remove from said file, said signal having a frequency above that of the range of human hearing.
16 . The method of claim 15 , wherein said signal has a frequency above about 20 kHz.
17 . A music player for playing an audio file containing a signal having a frequency above the range of human hearing, comprising:
a music player; and
a processor having a program that subtracts from said audio file, said signal that has a frequency above the range of human hearing.
18 . A system for transmission of audio files across a network, comprising:
a device for producing a digitized file containing an audio signal;
a digitized file containing a sample of digitized audio signal;
a sample containing a frequency above the range of human hearing;
a communication device to transmit said digitized file to a user; and
a player to play back said file, said player having a filter to remove from said file, said sample containing said frequency above the range of human hearing.
19 . The system of claim 18 , wherein said device for producing a digitized file includes an encrypter said file and said player includes a decrypter said file.