# phased.IsotropicHydrophone

Isotropic hydrophone

## Description

The `phased.IsotropicHydrophone` System object™ creates an isotropic hydrophone for sonar applications. An isotropic hydrophone has the same response in all signal directions. The response is the output voltage of the hydrophone per unit sound pressure. The response of a hydrophone is also called its sensitivity. You can specify the response using the `VoltageSensitivity` property.

To compute the response of a hydrophone for specified directions:

1. Define and set up an isotropic hydrophone System object. See Construction.

2. Call `step` to compute the response according to the properties of `phased.IsotropicHydrophone`.

Note

Instead of using the `step` method to perform the operation defined by the System object, you can call the object with arguments, as if it were a function. For example, `y = step(obj,x)` and `y = obj(x)` perform equivalent operations.

## Construction

`hydrophone = phased.IsotropicHydrophone` creates an isotropic hydrophone System object, `hydrophone`.

`hydrophone = phased.IsotropicHydrophone(Name,Value)` creates an isotropic hydrophone System object, with each specified property `Name` set to the specified `Value`. You can specify additional name-value pair arguments in any order as (`Name1,Value1`,...,`NameN,ValueN`).

## Properties

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Operating frequency range of hydrophone, specified as a real-valued 1-by-2 row vector of the form `[LowerBound HigherBound]`. This property defines the frequency range over which the hydrophone has a response. The hydrophone element has zero response outside this frequency range. Units are in Hz.

Example: `[0 1000]`

Data Types: `double`

Voltage sensitivity of hydrophone, specified as a scalar or real-valued 1-by-K row vector. When you specify the voltage sensitivity as a scalar, that value applies to the entire frequency range specified by `FrequencyRange`. When you specify the voltage sensitivity as a vector, the frequency range is divided into K-1 equal intervals. The sensitivity values are assigned to the interval end points. The `step` method interpolates the voltage sensitivity for any frequency inside the frequency range. Units are in dB//1V/μPa. See Hydrophone Sensitivity for more details.

Example: `10`

Data Types: `double`

Backbaffle hydrophone element, specified as `false` or `true`. Set this property to `true` to backbaffle the hydrophone. When the hydrophone is backbaffled, the hydrophone response for all azimuth angles beyond ±90° from broadside are zero. Broadside is defined as 0° azimuth and 0° elevation.

When the value of this property is `false`, the hydrophone is not backbaffled.

## Methods

Specific to `phased.IsotropicHydrophone` Object
`beamwidth`

Compute and display beamwidth of sensor element pattern

`directivity`

Directivity of isotropic hydrophone

`isPolarizationCapable`

Polarization capability

`pattern`

Plot isotropic hydrophone directivity and patterns

`patternAzimuth`

Plot isotropic hydrophone directivity and response patterns versus azimuth

`patternElevation`

Plot isotropic hydrophone directivity and response patterns versus elevation

`step`

Voltage sensitivity of isotropic hydrophone

Common to All System Objects
`release`

Allow System object property value changes

## Examples

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Examine the response and patterns of an isotropic hydrophone operating between 1 kHz and 10 kHz.

Set up the hydrophone parameters. Obtain the voltage sensitivity at five different elevation angles: ${-30}^{\circ }$, ${-15}^{\circ }$, ${0}^{\circ }$, ${15}^{\circ }$ and ${30}^{\circ }$. All azimuth angles are at ${0}^{\circ }$. The sensitivities are computed at the signal frequency of 2 kHz.

```hydrophone = phased.IsotropicHydrophone('FrequencyRange',[1 10]*1e3); fc = 2e3; resp = hydrophone(fc,[0 0 0 0 0;-30 -15 0 15 30]);```

Draw a 3-D plot of the voltage sensitivity.

```pattern(hydrophone,fc,[-180:180],[-90:90],'CoordinateSystem','polar', ... 'Type','powerdb')```

Examine the response and patterns of an isotropic hydrophone at three different frequencies. The hydrophone operates between 1 kHz and 10 kHz. Specify the voltage sensitivity as a vector.

Set up the hydrophone parameters and obtain the voltage sensitivity at 45° azimuth and 30° elevation. Compute the sensitivities at the signal frequencies of 2, 5, and 7 kHz.

```hydrophone = phased.IsotropicHydrophone('FrequencyRange',[1 10]*1e3, ... 'VoltageSensitivity',[-100 -90 -100]); fc = [2e3 5e3 7e3]; resp = hydrophone(fc,[45;30])```
```resp = 1×3 14.8051 29.2202 24.4152 ```

Draw a 2-D plot of the voltage sensitivity as a function of azimuth.

```pattern(hydrophone,fc,[-180:180],0,'CoordinateSystem','rectangular',... 'Type','power')```

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## References

[1] Urick, R.J. Principles of Underwater Sound. 3rd Edition. New York: Peninsula Publishing, 1996.

[2] Sherman, C.S., and J. Butler. Transducers and Arrays for Underwater Sound. New York: Springer, 2007.

[3] Allen, J.B., and D. Berkely. “Image method for efficiently simulating small-room acoustics”, Journal of the Acoustical Society of America. Vol. 65, No. 4. April 1979, pp. 943–950.

[4] Van Trees, H. Optimum Array Processing. New York: Wiley-Interscience, 2002, pp. 274–304.

## Extended Capabilities

Introduced in R2017a