unless the sotmd waves from the echosounder are be􀈸ng reflected

unless the sotmd waves from the echosounder are be􀈸ng reflected

from it ., As ultrasound has a high frequency, it has a short

wavelength and these small wav,􀈹s · are reflected well by small

objects such as fish.. Lower frequencies ·with e1eir larger

waves are not well reflected by fish'° This can be illustrated

by t..'1.e following example. If ocean waves hit against a

break.wall or vertical cliff they ·wil"l be reflected back again .,

However if the same waves hit a wharf pylon they will go around

it and very little of the wave wiJ.l be reflected. 'l'his is

pretty obvious but it does show that it is the relationship of

the size of the wave to the object it hits which deterraines how

much of the wave will be reflectedo

What is an echo sounder

Device used to measure depth of water

Short pulse sound energy transmitted vertically down

Time taken for it to echo back is used to determine depth