WAV File Post process

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Dear community,

My name is Rohith student at University of Freiberg, Germany. I came across in MATLA answers because I have problem to plot WAV files. I tried myself and looked in the documentation but I think I'm doing some mista. Here I attach two WAV files and Plots I got with code I use.ke:

WAV file:

Amplitude vs time

clear y Fs
info = audioinfo ( 'de ** av' )
[y, Fs] = audioread ( 'de *** v' );
t = 0: seconds (1 / Fs): seconds (info.Duration);
ylen = length (y);                   % signal length
t = (0: length (y) -1) / Fs;
plot (t * 1E + 3, y); % time vector
plot (t, y)
xlabel ( 'Time' )
ylabel ( 'amplitude' )

Frequency vs Magnitude (db)

clear, clc, close all
[x, fs] = audioread ( 'top081236.wav' );   % load an audio file
x = x (:, 1);                        % get the first channel
% determine the signal parameters
xlen = length (x);                   % signal length

t = (0: xlen-1) / fs;                  % time vector
% analysis parameters
wlen = 1024;                        % window length (recomended to be power of 2)
nfft = 2 * choose;                      % number of fft points (recomended to be power of 2)
hop = wlen / 2;                       % hop size
TimeRes = wlen / fs;                  % time result of the analysis (ie, window duration), s
FreqRes = 2 * fs / wlen;                % frequency resolution of the analysis (using Hanning window), Hz
% time-frequency grid parameters
TimeResGrid = hop / fs;               % time resolution of the grid, s
FreqResGrid = fs / nfft;              % frequency resolution of the grid, Hz
% perform spectral analysis
w2 = hanning (xlen, 'periodic' );
[PS, fX] = periodogram (x, w2, nfft, fs, 'power' );
Xamp = 20 * log10 (sqrt (PS) * sqrt (2));
% plot the spectrum
plot (fX, Xamp)
grid on
xlim ([0 max (fX)])
set (gca, 'FontName' , 'Times New Roman' , 'FontSize' , 12)
xlabel ( 'Frequency, Hz' )
ylabel ( 'Magnitude, dB' )
title ( 'Amplitude spectrum of the signal' )
%% mark the dominant frequencies in the spectrogram
% [~, inds] = max (Samp, [], 1);
% fmax = fS (inds);
% hold on
% plot3 (tS, fmax, zeros (length (tS)), 'r')