fix(uwa): surface reflection frequency units were wrong

arlpy/uwa.py

@@ -200,10 +200,11 @@ def bubble_surface_loss(windspeed, frequency, angle):
     -117.6
     """
     beta = _np.pi/2-angle
+    f = frequency/1000.0
     if windspeed >= 6:
-        a = 1.26e-3/_np.sin(beta) * windspeed**1.57 * frequency**0.85
+        a = 1.26e-3/_np.sin(beta) * windspeed**1.57 * f**0.85
     else:
-        a = 1.26e-3/_np.sin(beta) * 6**1.57 * frequency**0.85 * _np.exp(1.2*(windspeed-6))
+        a = 1.26e-3/_np.sin(beta) * 6**1.57 * f**0.85 * _np.exp(1.2*(windspeed-6))
     return 10**(-a/20.0)
 
 def bubble_soundspeed(void_fraction, c=soundspeed(), c_gas=340, relative_density=1000):
@@ -226,21 +227,21 @@ def bubble_soundspeed(void_fraction, c=soundspeed(), c_gas=340, relative_density
 
 def pressure(x, sensitivity, gain, volt_params=None):
     """Convert the real signal x to an acoustic pressure signal in micropascal.
-    
+
     :param x: real signal in voltage or bit depth (number of bits)
     :param sensitivity: receiving sensitivity in dB re 1V per micropascal
     :param gain: preamplifier gain in dB
-    :param volt_params: (nbits, v_ref) is used to convert the number of bits 
-        to voltage where nbits is the number of bits of each sample and v_ref 
-        is the reference voltage, default to None  
+    :param volt_params: (nbits, v_ref) is used to convert the number of bits
+        to voltage where nbits is the number of bits of each sample and v_ref
+        is the reference voltage, default to None
     :returns: acoustic pressure signal in micropascal
-    
+
     If `volt_params` is provided, the sample unit of x is in number of bits,
-    else is in voltage.  
+    else is in voltage.
 
-    >>> import arlpy 
+    >>> import arlpy
     >>> nbits = 16
-    >>> V_ref = 1.0 
+    >>> V_ref = 1.0
     >>> x_volt = V_ref*signal.cw(64, 1, 512)
     >>> x_bit = x_volt*(2**(nbits-1))
     >>> sensitivity = 0
@@ -251,17 +252,17 @@ def pressure(x, sensitivity, gain, volt_params=None):
     nu = 10**(sensitivity/20)
     G = 10**(gain/20)
     if volt_params is not None:
-        nbits, v_ref = volt_params   
+        nbits, v_ref = volt_params
         x = x*v_ref/(2**(nbits-1))
     return x/(nu*G)
 
 def spl(x, ref=1):
     """Get Sound Pressure Level (SPL) of the acoustic pressure signal x.
-    
+
     :param x: acoustic pressure signal in micropascal
     :param ref: reference acoustic pressure in micropascal, default to 1
     :returns: average SPL in dB re micropascal
-    
+
     In water, the common reference is 1 micropascal. In air, the common
     reference is 20 micropascal.
 

tests/test_basic.py

@@ -135,9 +135,9 @@ def test_bubble_resonance(self):
         self.assertApproxEqual(uwa.bubble_resonance(100e-6, depth=10), 45962)
 
     def test_bubble_surface_loss(self):
-        self.assertApproxEqual(utils.mag2db(uwa.bubble_surface_loss(3, 10000, 0)), -1.44, precision=2)
-        self.assertApproxEqual(utils.mag2db(uwa.bubble_surface_loss(6, 10000, 0)), -53)
-        self.assertApproxEqual(utils.mag2db(uwa.bubble_surface_loss(10, 10000, 0.785)), -166)
+        self.assertApproxEqual(utils.mag2db(uwa.bubble_surface_loss(15, 20000, 1.396)), -6.5, precision=1)
+        self.assertApproxEqual(utils.mag2db(uwa.bubble_surface_loss(10, 20000, 1.396)), -3.4, precision=1)
+        self.assertApproxEqual(utils.mag2db(uwa.bubble_surface_loss(5, 20000, 1.396)), -0.5, precision=1)
 
     def test_bubble_soundspeed(self):
         self.assertApproxEqual(uwa.bubble_soundspeed(0, 1500), 1500)
@@ -277,7 +277,7 @@ def test_detect_impulses(self):
         x += np.random.normal(0, 0.1, nsamp)
         ind_imp, _ = signal.detect_impulses(x, fs=100000, k=10, tdist=1e-3)
         self.assertArrayEqual(true_ind_imp, ind_imp)
-        
+
 class CommsTestSuite(MyTestCase):
 
     def test_random_data(self):