submitted

This commit is contained in:
aj 2020-11-09 19:26:23 +00:00
parent b2d3bccb29
commit 6e56067d1c
5 changed files with 131 additions and 23 deletions

View File

@ -457,8 +457,9 @@ literal "false"
\end_inset \end_inset
was used. was used.
Regular periodic frequencies in the time domain present as a peak in the Regular periodic frequencies in the time domain present as peaks in the
quefrency domain, this can also be achieved with an auto-corelation function. quefrency domain, these can also be identified with an auto-corelation
function.
The use of a low-pass filter was investigated in order to smooth the cepstrum The use of a low-pass filter was investigated in order to smooth the cepstrum
before programmatically finding pitch period candidates by applying before programmatically finding pitch period candidates by applying
\begin_inset Formula $x$ \begin_inset Formula $x$
@ -499,8 +500,8 @@ literal "false"
values. values.
Lowering the quefrency corresponds to an increase in frequency, thus it Lowering the quefrency corresponds to an increase in frequency, thus it
is reasonable to discard these values when 20 samples represents 1200Hz is reasonable to discard these values when 20 samples represents 1200Hz
sampled at 24kHz, a frequency higher than that of the fundamental frequency when sampled at 24kHz, a frequency higher than that of the fundamental
being investigated. frequency being investigated.
Additionally a minimum cepstrum threshold of 0.075 was used, from here the Additionally a minimum cepstrum threshold of 0.075 was used, from here the
quefrency candidate with the highest value was used as the pitch period. quefrency candidate with the highest value was used as the pitch period.
\end_layout \end_layout
@ -584,8 +585,8 @@ noprefix "false"
\end_inset \end_inset
. .
The frequency response for the filters these coefficients represent can The frequency response for similar filters of order 25 can be seen in figure
be seen in figure
\begin_inset CommandInset ref \begin_inset CommandInset ref
LatexCommand ref LatexCommand ref
reference "fig:stacked-spectra" reference "fig:stacked-spectra"
@ -1447,7 +1448,8 @@ hood_m
\begin_inset Caption Standard \begin_inset Caption Standard
\begin_layout Plain Layout \begin_layout Plain Layout
Order 20 LPC coefficients for both investigated samples Order 20 LPC coefficients for both investigated samples, source segments
taken from the first 100ms of each vowel sample
\begin_inset CommandInset label \begin_inset CommandInset label
LatexCommand label LatexCommand label
name "tab:Order-20-LPC-Coeffs" name "tab:Order-20-LPC-Coeffs"
@ -1598,8 +1600,8 @@ name "fig:stacked-spectra"
\end_layout \end_layout
\begin_layout Standard \begin_layout Standard
As the spectra are plotted with the same frequency bounds, the peaks of As the spectra are plotted with the same frequency axes bounds, the peaks
the filter response corresponding to estimations of the formant frequencies of the filter response corresponding to estimations of the formant frequencies
can be compared between the male and females voice. can be compared between the male and females voice.
In general the male's formant frequencies are lower than for the female's In general the male's formant frequencies are lower than for the female's
sample, this can be seen specifically with the first few peaks. sample, this can be seen specifically with the first few peaks.
@ -1714,12 +1716,103 @@ name "fig:Spectrum-Tile"
\end_layout \end_layout
\begin_layout Subsubsection
Source Segment Length Variation
\end_layout
\begin_layout Standard \begin_layout Standard
\begin_inset Flex TODO Note (inline) Figure
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:seg_length"
plural "false"
caps "false"
noprefix "false"
\end_inset
presents the speech sample and LPC filter spectral response for different
source sample lengths.
As the source sample length increases the spectral profile becomes less
smooth with higher peaks and deeper troughs throughout.
Additionally the mid to higher frequencies are affected more, the first
few formants are less affected.
\end_layout
\begin_layout Standard
\begin_inset Float figure
wide false
sideways false
status open status open
\begin_layout Plain Layout \begin_layout Plain Layout
segment length variation? \noindent
\align center
\begin_inset Graphics
filename /mnt/files/dev/matlab/lpss/resources/hood_m_25spect.png
lyxscale 10
width 25col%
\end_inset
\begin_inset Graphics
filename /mnt/files/dev/matlab/lpss/resources/hood_m_50spect.png
lyxscale 10
width 25col%
\end_inset
\begin_inset Graphics
filename /mnt/files/dev/matlab/lpss/resources/hood_m_100spect.png
lyxscale 10
width 25col%
\end_inset
\begin_inset Graphics
filename /mnt/files/dev/matlab/lpss/resources/hood_m_200spect.png
lyxscale 10
width 25col%
\end_inset
\end_layout
\begin_layout Plain Layout
\begin_inset Caption Standard
\begin_layout Plain Layout
Increasing source segment lengths for the
\begin_inset listings
lstparams "basicstyle={\ttfamily}"
inline true
status open
\begin_layout Plain Layout
hood_m
\end_layout
\end_inset
sample
\begin_inset CommandInset label
LatexCommand label
name "fig:seg_length"
\end_inset
\end_layout
\end_inset
\end_layout \end_layout
\end_inset \end_inset
@ -1775,7 +1868,7 @@ head_f
\begin_inset Formula $f_{1}$ \begin_inset Formula $f_{1}$
\end_inset \end_inset
as it did not refer to a peak in the way that would indicate a formant. as it did not refer to a maximum that would indicate a formant.
\end_layout \end_layout
\begin_layout Standard \begin_layout Standard
@ -2456,8 +2549,8 @@ noprefix "false"
When employing smoothing, the peak corresponding to the pitch period has When employing smoothing, the peak corresponding to the pitch period has
been amplified compared to the unsmoothed curve where the pitch period been amplified compared to the unsmoothed curve where the pitch period
does not reach far beyond the noise of the rest of the function. does not reach far beyond the noise of the rest of the function.
Following this, smoothing was employed when identifying the fundamental As a result of this, smoothing was employed in the following when identifying
frequency. the fundamental frequency.
\end_layout \end_layout
\begin_layout Standard \begin_layout Standard
@ -2544,8 +2637,8 @@ noprefix "false"
\end_inset \end_inset
. .
The identified pitch period, The identified quefrency pitch period,
\begin_inset Formula $t_{p}$ \begin_inset Formula $q_{p}$
\end_inset \end_inset
, and the corresponding fundamental frequency, , and the corresponding fundamental frequency,
@ -2577,7 +2670,7 @@ noprefix "false"
\begin_layout Standard \begin_layout Standard
\begin_inset Formula \begin_inset Formula
\[ \[
f_{f}=\frac{1}{\nicefrac{t_{p}}{f_{s}}} f_{f}=\frac{1}{\nicefrac{q_{p}}{f_{s}}}
\] \]
\end_inset \end_inset
@ -2795,8 +2888,8 @@ Synthesis
\end_layout \end_layout
\begin_layout Standard \begin_layout Standard
Following the convolution of the impulse train and the LPC filter, the synthesis Following the convolution of the impulse train and the LPC filter, the spectrogr
ed sound and the original can be seen presented in figure ams for the original and synthesised sound can be seen in figure
\begin_inset CommandInset ref \begin_inset CommandInset ref
LatexCommand ref LatexCommand ref
reference "fig:Spectrograms-synth" reference "fig:Spectrograms-synth"
@ -2808,8 +2901,8 @@ noprefix "false"
. .
The circled areas highlight similar portions, the formant frequencies can The circled areas highlight similar portions, the formant frequencies can
be seen in both. be seen as bright horizontal lines in both.
Despite being quasi-stationary, some variation in time can be seen for Despite being quasi-stationary, some variation in time can be seen throughout
the original signal. the original signal.
The stationary synthesised signal, however, has a flat profile in time. The stationary synthesised signal, however, has a flat profile in time.
\end_layout \end_layout
@ -2871,7 +2964,7 @@ buzzy
quality resembling a sawtooth wave of the same pitch as the original voice quality resembling a sawtooth wave of the same pitch as the original voice
sample. sample.
At these orders, the synthesised sound can not accurately be discerned At these orders, the synthesised sound can not accurately be discerned
as being speech. as speech.
As the filter order increases, the tone of the sound becomes less harsh As the filter order increases, the tone of the sound becomes less harsh
and by around order 20 the sample could be identified as being of a voice. and by around order 20 the sample could be identified as being of a voice.
By order 40, much of the harsh tone has been smoothed and the sample subjective By order 40, much of the harsh tone has been smoothed and the sample subjective
@ -2911,6 +3004,16 @@ The use of low-pass filtering on the cepstrum when identifying the fundamental
\end_layout \end_layout
\begin_layout Standard \begin_layout Standard
The relative frequencies for male and female speech was as expected with
the male speech segment having both lower fundamental frequencies and formant
frequencies.
\end_layout
\begin_layout Standard
\begin_inset Note Comment
status open
\begin_layout Plain Layout
A 100ms vowel segment sampled at 24kHz totals to 2,400 samples. A 100ms vowel segment sampled at 24kHz totals to 2,400 samples.
Assuming that each is represented by a float of 4 bytes, this uncompressed Assuming that each is represented by a float of 4 bytes, this uncompressed
vowel segment would fill 9600 bytes of storage. vowel segment would fill 9600 bytes of storage.
@ -2928,6 +3031,11 @@ literal "false"
. .
\end_layout \end_layout
\end_inset
\end_layout
\begin_layout Section \begin_layout Section
Conclusion Conclusion
\end_layout \end_layout
@ -2941,7 +3049,7 @@ Within this work, a complete source-filter model of speech has been presented,
final audio sample. final audio sample.
Various statistics about the original samples were calculated including Various statistics about the original samples were calculated including
the formant frequencies and the fundamental frequency. the formant frequencies and the fundamental frequency.
With a sufficient filter order, sound samples comparable to the originals With a sufficient filter order, sound samples comparable to human speech
were generated. were generated.
\end_layout \end_layout

Binary file not shown.

After

Width:  |  Height:  |  Size: 134 KiB

Binary file not shown.

After

Width:  |  Height:  |  Size: 142 KiB

Binary file not shown.

After

Width:  |  Height:  |  Size: 96 KiB

Binary file not shown.

After

Width:  |  Height:  |  Size: 113 KiB