[env_detec]Envelope Detections of signal #python #dsp

env_detect.py

"""1: Peak Detection"""

def envfol_peak_detection(sig, sr, chunk=4, order=6, lpfreq=150):
    """Envelope follower based on peak detection"""
    s = sig.shape[0] // chunk
    new_sig = np.array_split(np.abs(sig), s)
    result = []
    for i in new_sig:
        result.append(np.max(i))
    result = np.array(result)  
    nyq = 0.5 * sr
    normal_cutoff = lpfreq / nyq
    b, a = butter(order, normal_cutoff, btype='low', analog=False)
    result = lfilter(b, a, result)
    return result
  
  
"""2: Lowpass filter"""
def envfol_filter(sig, sr, smooth_sec=0.125):
    """Envelop follower based on lowpass filter. 
    
    Parameters
    ----------
    sig : numpy.ndarray
        signal array
    sr : int
        sampling rate
    smooth_sec : float
        Smoothing parameter in second. (sensitivity)

    Returns
    -------
    wav_env : numpy.ndarray
        Signal envelop in amplitude. 
    """
    smooth_hz = 1 / smooth_sec
    cutoff = smooth_hz/(sr / 2.)
    b, a = butter(1, cutoff, btype='low', analog=False)
    wav_env = np.sqrt(lfilter(b, a, sig*sig))  # Rectify signal
    return wav_env
  
 def convert_SPL(sig):
   	PA_ref = 20e-6
    SPL_dB = 20.0 * np.log((sig / PA_ref))
    return SPL_dB