ama                 package:seewave                 R Documentation

_A_m_p_l_i_t_u_d_e _m_o_d_u_l_a_t_i_o_n _a_n_a_l_y_s_i_s _o_f _a _t_i_m_e _w_a_v_e

_D_e_s_c_r_i_p_t_i_o_n:

     This function computes the Fourier analysis of a time wave
     envelope. This allows to detect periodicity, in particular those
     generated by amplitude modulations.

_U_s_a_g_e:

     ama(wave, f, wl, plot = TRUE, ...)

_A_r_g_u_m_e_n_t_s:

    wave: data describing the time wave.

       f: sampling frequency of 'wave'.

      wl: length of the window for the analysis (even number of
          points).

    plot: logical, if 'TRUE' the spectrum of the envelope  (by default
          'TRUE').

     ...: other 'meanspec' parameters.

_D_e_t_a_i_l_s:

     This function is based on 'oscillo' and 'meanspec'.
       The envelope of 'wave' is first computed and the spectrum of
     this envelope is then processed. All 'spec' and 'meanspec'
     arguments can be set up. Be sure to set up 'wl' large enough if
     you want to detect low amplitude modulation periodicity.

_V_a_l_u_e:

     If 'plot' is 'FALSE', 'ama' returns  a vector of numeric data
     corresponding to the computed spectrum. If 'peaks' is 'TRUE',
     'spec' returns a list with two elements: 

    spec: the spectrum computed

  peaks : the peaks values (in kHz).

_A_u_t_h_o_r(_s):

     Jrme Sueur jerome.sueur@ibaic.u-psud.fr

_S_e_e _A_l_s_o:

     'oscillo'

_E_x_a_m_p_l_e_s:

     data(orni)
     # detection of 2 main amplitude modulations in a cicada song:
     # one with a 0.020 kHz frequency (due to signal/silence periodicity)
     # one with a 0.258 kHz frequency (due to pulses in the echemes)
     # one with a 2.369 kHz frequency (fundamental frequency)
     ama(orni,f=22050,wl=1024,type="l")
     # these amplitude modulations can be identify with a cursor:
     ama(orni,f=22050,wl=1024,type="l",identify=TRUE)

