get y values of z values in spectrogram

Hii there. I want to get the y-values for specific z-values from a spectrogram. I just want to get the y-values for (z > -10).

This is my code for plot the spectrogram:

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% load a signal

[x, fs] = audioread('file.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 = 4*wlen; % number of fft points (recomended to be power of 2)

hop = wlen/4; % hop size

TimeRes = wlen/fs; % time resulution of the analysis (i.e., 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 STFT

w1 = hanning(wlen, 'periodic');

[~, fS, tS, PSD] = spectrogram(x, w1, wlen-hop, nfft, fs);

Samp = 20*log10(sqrt(PSD.*enbw(w1, fs))*sqrt(2));

% plot the spectrogram

figure;

surf(tS, fS, Samp);

shading interp;

axis tight;

box on;

set(gca, 'FontName', 'Times New Roman', 'FontSize', 12);

ylim([0 1500]);

xlim([0 2]);

xlabel('Time, s');

ylabel('Frequency, Hz');

title('Unterarm Messung Ruhepuls');

view(0, 90);

colormap('jet');

hcol = colorbar;

set(hcol, 'FontName', 'Times New Roman', 'FontSize', 12)

ylabel(hcol, 'Magnitude, dB')

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