Well logging system employing average travel time computation

Claim 1

AN ACOUSTIC LOGGING SYSTEM FOR USE IN A WELL BORE COMPRISING: A BOREHOLE INSTRUMENT SIZED FOR PASSAGE THROUGH A WELL BORE AND HAVING SPACED UPPER AND LOWER ACOUSTIC TRANSMITTER MEANS AND AT LEAST TWO ACOUSTIC RECEIVER MEANS THEREBETWEEN, SIGNAL OUTPUT CHANNEL MEANS IN SAID INSTRUMENT FOR COUPLING SIGNALS FOR TRANSMISSION TO THE EARTH''S SURFACE, MEANS COUPLING SAID TRANSMITTER MEANS, SAID RECEIVER MEANS, AND SAID SIGNAL OUTPUT CHANNEL MEANS FOR DEVELOPING IN SAID SIGNAL OUTPUT CHANNEL MEANS A SIGNAL REPRESENTATION OF AN INDIVIDUAL ENERGY BETER-TO-RECEIVER ACOUSTIC TRAVEL TIME OF ACOUSITIC ENERGY BETWEEN EACH OF SAID TRANSMITTER MEANS AND EACH OF SAID RECIEVER MEANS, FOR SUCCESSIVE DEPTH INTERVALS, MEANS FOR TRANSMITTING SAID SIGNALS TO THE EARTH''S SURFACE, MEANS AT THE EARTH''S SURFACE RESPONSIVE TO SAID SIGNALS TO COMBINE THE TRAVEL TIMES REPRESENTED BY SAID SIGNALS AND PROVIDE AVERAGE TIME MEASUREMENT OF THE TAVEL TIME OF ACOUSTIC ENERGY BETWEEN SAID RECEIVER MEANS, AND MEANS COUPLED TO SAID COMBINING MEANS TO RECORD SAID AVERAGE TIME MEASURMENTS AS A FUNCTION OF DEPTH.