Method and apparatus for monitoring sound-conducting media

Claim 1

A method of monitoring vibration characteristics of sound-conducting media, comprising the steps of: providing at least one sound-conducting medium; transmitting sound vibrations to the sound-conducting medium; controlling the frequency of the transmitted sound vibrations so as to periodically pass through a predetermined frequency range during successive frequency throughpass periods separated by interval periods during which the transmission of the sound to the medium is interrupted; receiving the returned frequency spectrum of the sound vibrations at the sound-conducting medium; comparing the amplitude course or phase course of the received sound vibrations during a given evaluation period comprising a frequency throughpass period and an interval period with the amplitude course or phase course during a preceding evaluation period; each said evaluation period being larger than the frequency throughpass period; and triggering an alarm when there are present deviations of both amplitude courses or both phase courses from one another due to a sudden change of the vibration resonance spectrum of the sound-conducting media.

Claim 2

A method of monitoring vibration characteristics of sound-conducting media, comprising the steps of: providing at least one sound-conducting medium; transmitting sound vibrations to the sound-conducting medium; controlling the frequency of the transmitted sound vibrations so as to periodically pass through a predetermined frequency range during successive frequency throughpass periods separated by interval periods during which the transmission of the sound to the medium is interrupted; receiving the returned frequency spectrum of the sound vibrations at the sound-conducting medium; comparing the amplitude course or phase course of the received sound vibrations during a given evaluation period comprising a frequency throughpass period and an interval period with the amplitude course or phase course during a preceding evaluation period; each said evaluation period being larger than the frequency throughpass period; and triggering an alarm when there are present deviations of both amplitude courses or both phase courses from one another due to a sudden change of the vibration resonance spectrum of the sound-conducting media.

Claim 12

An apparatus for monitoring vibration characteristics of sound-conducting media comprising: sound transmitter means for delivering sound vibrations to a monitored medium; means for the periodic continuous change of the frequency of the sound vibrations during each of successive frequency throughpass periods for controlling the sound transmitting means, said frequency throughpass periods being separated by interval periods during which the transmission of sound vibrations is interrupted; sound receiver means for taking-up the sound vibrations and converting such into an electrical signal; an electro-acoustical transducer simultaneously serving as the sound transmitter means and sound receiver means; an evaluation circuit for comparing the amplitude course or phase course of the taken-up sound vibrations during an evaluation period comprising a frequency throughpass period and an interval period with the course of the amplitude or phase during a previous evaluation period; reversing switch means for periodically alternately connecting, during a predetermined time duration, the frequency change means with the electro-acoustical transducer, and during a further predetermined time connecting the evaluation circuit with the electro-acoustical transducer and disconnecting the frequency change means; the switching period of the reversing switch means being equal to the evaluation period; an alarm device; and said evaluation circuit controlling the alarm device when there exists a predetermined difference between the respective amplitude course of respective phase course of both evaluation periods due to a sudden change of the vibration resonance spectrum of the sound-conducting media.

Claim 13

An apparatus for monitoring vibration characteristics of sound-conducting media comprising: sound transmitter means for delivering sound vibrations to a monitored medium; means for the periodic continuous change of the frequency of the sound vibrations during each of successive frequency throughpass periods for controlling the sound transmitting means, said frequency throughpass periods being separated by interval periods during which the transmission of sound vibrations is interrupted; sound receiver means for taking-up the sound vibrations and converting such into an electrical signal; an electro-acoustical transducer simultaneously serving as the sound transmitter means and sound receiver means; an evaluation circuit for comparing the amplitude course or phase course of the taken-up sound vibrations during an evaluation period comprising a frequency throughpass period and an interval period with the course of the amplitude or phase during a previous evaluation period; reversing switch means for periodically alternately connecting, during a predetermined time duration, the frequency change means with the electro-acoustical transducer, and during a further predetermined time connecting the evaluation circuit with the electro-acoustical transducer and disconnecting the frequency change means; the switching period of the reversing switch means being equal to the evaluation period; an alarm device; and said evaluation circuit controlling the alarm device when there exists a predetermined difference between the respective amplitude course of respective phase course of both evaluation periods due to a sudden change of the vibration resonance spectrum of the sound-conducting media.