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      <h1>Seawater Sound Absorption</h1>
      <small class="dont-index">Source: <a href="https://github.com/dankelley/oce/blob/HEAD/R/sw.R" class="external-link"><code>R/sw.R</code></a></small>
      <div class="d-none name"><code>swSoundAbsorption.Rd</code></div>
    </div>

    <div class="ref-description section level2">
    <p>Compute the sound absorption of seawater, in dB/m</p>
    </div>

    <div class="section level2">
    <h2 id="ref-usage">Usage<a class="anchor" aria-label="anchor" href="#ref-usage"></a></h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span><span class="fu">swSoundAbsorption</span><span class="op">(</span></span>
<span>  <span class="va">frequency</span>,</span>
<span>  <span class="va">salinity</span>,</span>
<span>  <span class="va">temperature</span>,</span>
<span>  <span class="va">pressure</span>,</span>
<span>  pH <span class="op">=</span> <span class="fl">8</span>,</span>
<span>  formulation <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">"fisher-simmons"</span>, <span class="st">"francois-garrison"</span><span class="op">)</span></span>
<span><span class="op">)</span></span></code></pre></div>
    </div>

    <div class="section level2">
    <h2 id="arguments">Arguments<a class="anchor" aria-label="anchor" href="#arguments"></a></h2>


<dl><dt id="arg-frequency">frequency<a class="anchor" aria-label="anchor" href="#arg-frequency"></a></dt>
<dd><p>The frequency of sound, in Hz.</p></dd>


<dt id="arg-salinity">salinity<a class="anchor" aria-label="anchor" href="#arg-salinity"></a></dt>
<dd><p>either practical salinity (in which case <code>temperature</code>
and <code>pressure</code> must be provided) <em>or</em> an <code>oce</code> object, in
which case <code>salinity</code>, <code>temperature</code> (in the ITS-90 scale; see
next item), etc. are inferred from the object, ignoring the
other parameters, if they are supplied.</p></dd>


<dt id="arg-temperature">temperature<a class="anchor" aria-label="anchor" href="#arg-temperature"></a></dt>
<dd><p><em>in-situ</em> temperature (\(^\circ\)C), defined
on the ITS-90 scale.  This scale is used by GSW-style calculation (as
requested by setting <code>eos="gsw"</code>), and is the value contained within
<code>ctd</code> objects (and probably most other objects created with data
acquired in the past decade or two). Since the UNESCO-style calculation is
based on IPTS-68, the temperature is converted within the present function,
using <code><a href="T68fromT90.html">T68fromT90()</a></code>.</p></dd>


<dt id="arg-pressure">pressure<a class="anchor" aria-label="anchor" href="#arg-pressure"></a></dt>
<dd><p>pressure (dbar)</p></dd>


<dt id="arg-ph">pH<a class="anchor" aria-label="anchor" href="#arg-ph"></a></dt>
<dd><p>seawater pH</p></dd>


<dt id="arg-formulation">formulation<a class="anchor" aria-label="anchor" href="#arg-formulation"></a></dt>
<dd><p>character string indicating the formulation to use, either
of <code>"fischer-simmons"</code> or <code>"francois-garrison"</code>; see “References”.</p></dd>

</dl></div>
    <div class="section level2">
    <h2 id="value">Value<a class="anchor" aria-label="anchor" href="#value"></a></h2>
    <p>Sound absorption in dB/m.</p>
    </div>
    <div class="section level2">
    <h2 id="details">Details<a class="anchor" aria-label="anchor" href="#details"></a></h2>
    <p>Salinity and pH are ignored in this formulation.  Several formulae may be
found in the literature, and they give results differing by 10 percent, as
shown in reference 3 for example.  For this reason, it is likely that more
formulations will be added to this function, and entirely possible that the
default may change.</p>
    </div>
    <div class="section level2">
    <h2 id="references">References<a class="anchor" aria-label="anchor" href="#references"></a></h2>

<ol><li><p>F. H. Fisher and V. P. Simmons, 1977.  Sound absorption in
sea water.  Journal of the Acoustical Society of America, 62(3), 558-564.</p></li>
<li><p>R. E. Francois and G. R. Garrison, 1982.  Sound absorption based on
ocean measurements.  Part II: Boric acid contribution and equation for total
absorption.  Journal of the Acoustical Society of America, 72(6):1879-1890.</p></li>
<li><p><code>http://resource.npl.co.uk/acoustics/techguides/seaabsorption/</code></p></li>
</ol></div>
    <div class="section level2">
    <h2 id="see-also">See also<a class="anchor" aria-label="anchor" href="#see-also"></a></h2>
    <div class="dont-index"><p>Other functions that calculate seawater properties:
<code><a href="T68fromT90.html">T68fromT90</a>()</code>,
<code><a href="T90fromT48.html">T90fromT48</a>()</code>,
<code><a href="T90fromT68.html">T90fromT68</a>()</code>,
<code><a href="computableWaterProperties.html">computableWaterProperties</a>()</code>,
<code><a href="locationForGsw.html">locationForGsw</a>()</code>,
<code><a href="swAbsoluteSalinity.html">swAbsoluteSalinity</a>()</code>,
<code><a href="swAlpha.html">swAlpha</a>()</code>,
<code><a href="swAlphaOverBeta.html">swAlphaOverBeta</a>()</code>,
<code><a href="swBeta.html">swBeta</a>()</code>,
<code><a href="swCSTp.html">swCSTp</a>()</code>,
<code><a href="swConservativeTemperature.html">swConservativeTemperature</a>()</code>,
<code><a href="swDepth.html">swDepth</a>()</code>,
<code><a href="swDynamicHeight.html">swDynamicHeight</a>()</code>,
<code><a href="swLapseRate.html">swLapseRate</a>()</code>,
<code><a href="swN2.html">swN2</a>()</code>,
<code><a href="swPressure.html">swPressure</a>()</code>,
<code><a href="swRho.html">swRho</a>()</code>,
<code><a href="swRrho.html">swRrho</a>()</code>,
<code><a href="swSCTp.html">swSCTp</a>()</code>,
<code><a href="swSR.html">swSR</a>()</code>,
<code><a href="swSTrho.html">swSTrho</a>()</code>,
<code><a href="swSigma.html">swSigma</a>()</code>,
<code><a href="swSigma0.html">swSigma0</a>()</code>,
<code><a href="swSigma1.html">swSigma1</a>()</code>,
<code><a href="swSigma2.html">swSigma2</a>()</code>,
<code><a href="swSigma3.html">swSigma3</a>()</code>,
<code><a href="swSigma4.html">swSigma4</a>()</code>,
<code><a href="swSigmaT.html">swSigmaT</a>()</code>,
<code><a href="swSigmaTheta.html">swSigmaTheta</a>()</code>,
<code><a href="swSoundSpeed.html">swSoundSpeed</a>()</code>,
<code><a href="swSpecificHeat.html">swSpecificHeat</a>()</code>,
<code><a href="swSpice.html">swSpice</a>()</code>,
<code><a href="swSpiciness0.html">swSpiciness0</a>()</code>,
<code><a href="swSpiciness1.html">swSpiciness1</a>()</code>,
<code><a href="swSpiciness2.html">swSpiciness2</a>()</code>,
<code><a href="swSstar.html">swSstar</a>()</code>,
<code><a href="swTFreeze.html">swTFreeze</a>()</code>,
<code><a href="swTSrho.html">swTSrho</a>()</code>,
<code><a href="swThermalConductivity.html">swThermalConductivity</a>()</code>,
<code><a href="swTheta.html">swTheta</a>()</code>,
<code><a href="swViscosity.html">swViscosity</a>()</code>,
<code><a href="swZ.html">swZ</a>()</code></p></div>
    </div>
    <div class="section level2">
    <h2 id="author">Author<a class="anchor" aria-label="anchor" href="#author"></a></h2>
    <p>Dan Kelley</p>
    </div>

    <div class="section level2">
    <h2 id="ref-examples">Examples<a class="anchor" aria-label="anchor" href="#ref-examples"></a></h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="co"># Fisher &amp; Simmons (1977 table IV) gives 0.52 dB/km for 35 PSU, 5 degC, 500 atm</span></span></span>
<span class="r-in"><span><span class="co"># (4990 dbar of water)a and 10 kHz</span></span></span>
<span class="r-in"><span><span class="va">alpha</span> <span class="op">&lt;-</span> <span class="fu">swSoundAbsorption</span><span class="op">(</span><span class="fl">35</span>, <span class="fl">4</span>, <span class="fl">4990</span>, <span class="fl">10e3</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="co"># reproduce part of Fig 8 of Francois and Garrison (1982 Fig 8)</span></span></span>
<span class="r-in"><span><span class="va">f</span> <span class="op">&lt;-</span> <span class="fl">1e3</span> <span class="op">*</span> <span class="fl">10</span><span class="op">^</span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/seq.html" class="external-link">seq</a></span><span class="op">(</span><span class="op">-</span><span class="fl">1</span>, <span class="fl">3</span>, <span class="fl">0.1</span><span class="op">)</span><span class="op">)</span> <span class="co"># in KHz</span></span></span>
<span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/graphics/plot.default.html" class="external-link">plot</a></span><span class="op">(</span><span class="va">f</span> <span class="op">/</span> <span class="fl">1000</span>, <span class="fl">1e3</span> <span class="op">*</span> <span class="fu">swSoundAbsorption</span><span class="op">(</span><span class="va">f</span>, <span class="fl">35</span>, <span class="fl">10</span>, <span class="fl">0</span>, formulation <span class="op">=</span> <span class="st">"fr"</span><span class="op">)</span>,</span></span>
<span class="r-in"><span>    xlab <span class="op">=</span> <span class="st">" Freq [kHz]"</span>, ylab <span class="op">=</span> <span class="st">" dB/km"</span>, type <span class="op">=</span> <span class="st">"l"</span>, log <span class="op">=</span> <span class="st">"xy"</span></span></span>
<span class="r-in"><span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/graphics/lines.html" class="external-link">lines</a></span><span class="op">(</span><span class="va">f</span> <span class="op">/</span> <span class="fl">1000</span>, <span class="fl">1e3</span> <span class="op">*</span> <span class="fu">swSoundAbsorption</span><span class="op">(</span><span class="va">f</span>, <span class="fl">0</span>, <span class="fl">10</span>, <span class="fl">0</span>, formulation <span class="op">=</span> <span class="st">"fr"</span><span class="op">)</span>, lty <span class="op">=</span> <span class="st">"dashed"</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/graphics/legend.html" class="external-link">legend</a></span><span class="op">(</span><span class="st">"topleft"</span>, lty <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">"solid"</span>, <span class="st">"dashed"</span><span class="op">)</span>, legend <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">"S=35"</span>, <span class="st">"S=0"</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-plt img"><img src="swSoundAbsorption-1.png" alt="" width="700" height="700"></span>
<span class="r-in"><span></span></span>
</code></pre></div>
    </div>
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