From 12d4d854b02e9e65e299bf1f534fe7e4dec34485 Mon Sep 17 00:00:00 2001
From: topherbuckley <topherbuckley@gmail.com>
Date: Wed, 28 Feb 2018 10:36:20 +0900
Subject: [PATCH 1/2] Fixes exponential weighting filter implementation. See
 Issue #210

---
 acoustics/standards/iec_61672_1_2013.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/acoustics/standards/iec_61672_1_2013.py b/acoustics/standards/iec_61672_1_2013.py
index 25de534e..1888a6bd 100644
--- a/acoustics/standards/iec_61672_1_2013.py
+++ b/acoustics/standards/iec_61672_1_2013.py
@@ -157,8 +157,9 @@ def integrate(data, sample_frequency, integration_time):
     integration_time = np.asarray(integration_time)
     sample_frequency = np.asarray(sample_frequency)
     samples = data.shape[-1]
-    b, a  = zpk2tf([1.0], [1.0, integration_time], [1.0])
-    b, a = bilinear(b, a, fs=sample_frequency)
+    b_analog = np.poly1d([1])
+    a_analog = np.poly1d([integration_time, 1])
+    b, a = bilinear(b_analog, a_analog, fs=sample_frequency)
     #b, a = bilinear([1.0], [1.0, integration_time], fs=sample_frequency) # Bilinear: Analog to Digital filter.
     n = np.floor(integration_time * sample_frequency).astype(int)
     data = data[..., 0:n*(samples//n)]

From a937cd7f0cec7d38194b810439fcb3bde0befc28 Mon Sep 17 00:00:00 2001
From: topherbuckley <topherbuckley@gmail.com>
Date: Thu, 1 Mar 2018 10:12:59 +0900
Subject: [PATCH 2/2] added kwarg for reference pressure pref in order to be
 able to calculate spectrograms on dB SPL scale

---
 acoustics/_signal.pyx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/acoustics/_signal.pyx b/acoustics/_signal.pyx
index 64faedec..c7f2f9d7 100644
--- a/acoustics/_signal.pyx
+++ b/acoustics/_signal.pyx
@@ -651,6 +651,7 @@ class Signal(numpy.ndarray):
         * xlim
         * ylim
         * clim
+        * pref (default to 1, set pref=20e-6 for SPL)
         .. note:: This method only works for a single channel.
 
         """
@@ -659,6 +660,7 @@ class Signal(numpy.ndarray):
             'xlim' : None,
             'ylim' : None,
             'clim' : None,
+            'pref' : 1,
             'NFFT' : 4096,
             'noverlap' : 128,
             'title': 'Spectrogram',
@@ -676,7 +678,7 @@ class Signal(numpy.ndarray):
         ax0 = params.get('ax', plt.figure().add_subplot(111))
         ax0.set_title(params['title'])
 
-        data = np.squeeze(self)
+        data = np.squeeze(self) / pref
         try:
             _, _, _, im = ax0.specgram(data, Fs=self.fs, noverlap=params['noverlap'], NFFT=params['NFFT'], mode='magnitude', scale_by_freq=False)
         except AttributeError: