# Sound Transmission loss in water

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#### afr123

##### Junior Member level 1
Hi,

I measured the sound pressure levels at different distances using hydrophone as a receiver. Now I want to know where the transmission loss due to spreading is spherical, cylindrical or between the two from the measured data.

My data is in volts which can be converted to Pressure using Receive Sensitivity of the hydrophone.

My question is how would I know from the measured data where the Transmission loss is due to spherical or cylindrical?

Regards

#### barry

I don't know anything about sound transmission through water, so let me give you my expert opinion: Wouldn't it depend on the source? Also, I don't think you can you can infer a 3-dimensional parameter (the spreading) using a zero-dimensional sensor (your hydrophone).

#### FvM

##### Super Moderator
Staff member
Transmission loss is due to spherical or cylindrical?
Means what? Sound waves in fluids are pressure waves, if the transducer is small compared to wavelength, it will emit "omnidirectional" spherical waves from the start. Respectively the sound pressure decays with 1/r. At higher frequencies, sound absorption has to be considered for large distance transmission.

#### Kajunbee

I know nothing of sound transmission through air or water but I understand where Barry's coming from. I would think spherical and cylindrical would have to be worked out from the initial energy and position of the source. But what do I know. If you search " sonar propagation" you'll probably find all the information you need and then some.

#### c_mitra

If the source and detector are close enough (say of the order of the wave length), then the response will depend on the source geometry and construction; at large distances, the asymmetry will be maintained but you can use inverse square rule.

The absorption by water will depend on the wavelength and that will be determined by some log function (exponential decay).

It is wrong to say "Transmission loss is due to spherical or cylindrical" because absorption of energy has nothing to do with the coordinate frame used; you decide on a model and use the suitable frame of reference.

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