Try this:
% Initialization steps.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 15;
% read file into memory */
[wave, fs]=audioread('1.wav');
% sound(wave, fs); % see what it sounds like */
t=0:1/fs:(length(wave)-1)/fs; % and get sampling frequency */
subplot(3, 1, 1)
%plot(t,wave)
plot(t, wave, 'b-');
title('Wave File', 'FontSize', fontSize);
ylabel('Amplitude', 'FontSize', fontSize);
xlabel('Length (in seconds)', 'FontSize', fontSize);
grid on;
L = length(wave);
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y = fft(wave,NFFT)/L;
f = fs/2*linspace(0,1,NFFT/2+1);
% Plot single-sided amplitude spectrum.
subplot(3, 1, 2);
y = 2*abs(Y(1:NFFT/2+1));
plot(f, y, 'b-');
title('Single-Sided Amplitude Spectrum of y(t)', 'FontSize', fontSize);
xlabel('Frequency (Hz)', 'FontSize', fontSize);
ylabel('|Y(f)|', 'FontSize', fontSize);
grid on;
subplot(3, 1, 3);
y = 2*abs(Y(1:NFFT/2+1));
plot(f, y, 'b-');
title('Single-Sided Amplitude Spectrum of y(t)', 'FontSize', fontSize);
xlabel('Frequency (Hz)', 'FontSize', fontSize);
ylabel('|Y(f)|', 'FontSize', fontSize);
grid on;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0.04, 1, 0.96]);
xlim([0, 400]);
% Smooth with a Savitzky Golay Filter
smoothy = sgolayfilt(y, 2, 101);
hold on;
plot(f, smoothy, 'r-', 'LineWidth', 2);
% Get the upper envelope
uppery = movmax(y,51);
% Smooth it out some
windowWidth = 31;
uppery = conv(uppery, ones(windowWidth, 1)/windowWidth, 'same');
plot(f, uppery, 'r-', 'LineWidth', 2);
