1. Explain the significance of ensuring that the echo sounder always provide correct and reliable information?
Answers
Answer:
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Explanation:
Echo-sounders transmit a pulse of acoustic energy down towards the seabed and measure the total time taken for it to travel through the water, i.e. the outwards and return journey. If the measured time is one second and it is known that the speed of acoustic waves is 1500 m/s, the depth is obviously (1500 x 1)/2 metres = 750 m.
By using a recorder with slowly moving paper to display the time of transmission and then the echoes as they return, a past history of the depth and of the sea bed topography is built up. If the system is sufficiently sensitive it will also display the echoes from fish, but this gives merely an indication of their relative abundance. Instruments capable of making quantitative acoustic measurements are needed, together with methods of turning these into figures of the absolute fish abundance. To do this, echo-sounders with precise characteristics have evolved. Their signals are coupled to a specially developed instrument, the echo-integrator, which selects and processes them in various ways. In this section we first consider the echo-sounder.