The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

September, 1921 for this position of his head the ob- pect, producing the. sound yi). be brought into his best field of vision, The relative location of the eyes with respect to the two ears, brought about through the processes of evolution, has apparently been determined by the fact that the sense of direction, the bin- aural sense, is most acute for directions perpendicular to the line joining the two ears. It also is to be noticed that, other things being equal, the accuracy of the binaural sense is proportional to the distance between the two ears. <A person or animal having the two ears widely spaced. has an advantage, so far as the determination of direction is concerned, over his "narrow minded" brethren. It will be noted later that the MV hydrophone takes advantage of this. fact, Although the binaural principle has been recognized for a number of years, its high state of development in human beings and many animals has not been recognized. The high state of develop- 'ment of this sense may be appreciated from the fact that the average person, in judging .the direction of a sound 'determines the time. difference between reception of the sound: at his two ears to within a hundred-thousandth of a second and a trained listener probably determines this time difference to with- in five-millionths of a second. The binaural sense, then, is a sense of direction of sounds brought about by the difference in time of reception of the sound at the two ears. This sense, which is continually operating, and upon which our safety in a large measure depends, has been developed through the processes of evolution to an extremely high degree of perfection. Any sound-detecting device that de- termines direction through the opera- tion of this sense is said to operate - on the "binaural principle". The MV hydrophone makes use of the "binaural principle' for the determination of direction. ay Compensating the Differences The ears have certain advantages over other types of sotind - detecting devices, the chief one of which is they are readily portable. As a result, they operate conveniently on the binaural Principle because with a minimum of effort they can be brought into such a Position with respect to a sound that the direction of the sound will be normal to the line joining them, this being the position where the sound appears to be "binaurally centered", that is, does not appear to be either to the right or to the left, and where direction is determined with greatest accuracy. - Neglecting the possible effect on the rival +e "has at times certain disadvantages, the MARINE REVIEW listener's features,* one can conceive of ways. other than by turning his head whereby he could binaurally cen- ter a sound and thereby determine its direction, - If -we:-remember that 2 sound is binaurally centered when the impression of the sound entering the two ears registers simultaneously on the listener's brain, then, instead of turning the head unk this condition is reached, one can conceive of an individual having ears that can move in or out from their normal position. Suppose such an individual heard a sound somewhere to his right. If his binaural sense were normal, this would - imply that the sound reached his right ear first, Or, more particularly, that the sound entering his right ear reg- istered first on his brain. Now, with- out turning his head, he could cause the sound impression at both ears to register simultaneously by delaying the time of transit of the sound from the outer ear to the brain in case of the right. ear, or by decreasing the time of transit in case of the left ear, or by causing such variations to oper- ate by a definite and proper amount in both ears simultaneously. This effect could be brought about by extending the right ear and with- drawing the left ear a proper amount from their normal position, or by leav- ing. both ears in their normal position and imposing a proper amount of time lag and acceleration upon the nerve transmitting .mechanism of the right and left ear respectively. In either case the process of binaurally center- ing the sound without moving the re- ceivers would be '¢alled "compensation" Compensation, then is the process of mechanically. prow lucing at will a varia- tion; in: the relative time of arrival of sound impulses. cat the two ears in such a manner aind by such an amount that the impulses register simultan- eously, giving' the listener the impres- sion the sound is' neither to his right nor. his. leit, The design of the MV hydeasidae is such that the process of compensation can be employed 'to binaurally center a sound from any direction, enabling the listener to determine its direction. | The particular part of the device used 'for varying the relative time of ar- of sound to the two ears is termed a "compensator". As a sound detecting device, the ear chief one of which is it is nonfocusing, or non-selective. It receives sound from all directions with equal intensity. Ofttimes it would be a convenience if -- the ears could be focused to receive sound from a definite direction and at the same time made insensitive to sounds from other directions. Under such conditions, it would be possible 'One of the most 405 to follow the conversation of any one individual in a gathering of people, all of whom are conversing. One can readily conceive of an in- dividual endowed with such hearing powers. If, instead of one ear on each side of his head, he could have several extending outward on each side along a line passing through the two ears, and if the time of transit of the sound from each ear were compensated so that the impressions from all the ears would reach the brain simultaneously for sound approaching the line of re- ceivers or ears from some definite di- rection, then he could hear sensitively any sounds approaching from this di- rection, since the impressions from all ears would arrive in phase and there- fore add, while sounds from any other direction would not be distinctly heard, due to the fact that the responses from the different ears would' arrive out of phase and would then tend to cancel one another through the process of Wave interference, The MV hydrophone is a sound-re- ceiving device employing a number of receivers and carrying a compensat- ing device such that the sound ré- sponses from all the receivers can be made to reach the listener's ears in phase for sound approaching from any direction. This results in giving the device a high degree of selectivity, that is, the ability to hear sensitivély sound from any desired direction and at the same time insensitively sound from every other direction. : Pi Sieicn Would Enlarge Termin al F acilities The harbor board of Houston, Tex. has recommended a bond issue of $1,- 250,000 to be used in the construc- tion of additional terminal. facilities at the turning basin of the Houston ship channel. The Houston mayor and - commissioners are known to _ favor this bond issue and it will be sub- mitted to the voters at an early date. The harbor board also ask permission to borrow $180,000 from local banks to make additional improvements on certain docks. It is declared these handle three times as much cotton as improvements will enable the port to previously and will also increase the revenue 25 per cent. The commis- sioners adopted resolutions endorsing this proposition of the harbor board. important improve- ments recommended by the harbor board is the construction of additional links and other trackage of the muni- cipal belt railway, which serves most of the industries on the Houston ship channel.