IRJET- Comparative Analysis of Emotion Recognition System

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 12 | Dec 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 380
Comparative Analysis of Emotion Recognition System
Chinmay Thakare1, Neetesh Kumar Chaurasia2, Darshan Rathod3, Gargi Joshi4,
Santwana Gudadhe5
1,2,3,4,5Dept. of Computer Engineering, Pimpri Chinchwad College of Engineering, Pune, India
--------------------------------------------------------------***--------------------------------------------------------------
Abstract - Speech carries a lot more deal of information
for emotion recognition. This paper discussed the
implementation of emotion recognition system on SAVEE
dataset. Emotion recognition system deals with speech
input. Various features like MFCC, contrast, mel frequency,
tonnetz and chroma are considered from input dataset. This
paper presents a comparative analysis of speech emotion
recognition system with CNN, RFC, XGBoost and SVM
classifier. In all CNN model give highest accuracy for MFCC
feature. The study is aimed at exploring the dependencies
that exist with the human emotional state. We trained and
tested the model with a CNN, RFC, XGBoost and SVM
classifier and processed the audio clips to characterize them
into 7 significant emotions.
Keywords: SAVEE, CNN, SVM, Speech Emotion Recognition,
SER, MFCC
1. INTRODUCTION
Emotion recognition using human speech input, is one of
the most trending fields in speech analysis as well as
emotion recognition. Speech signal is information rich and
and non traditional approach to the problem. The speech
signal is just as important as graphical in emotion
recognition in nature. Features in speech are perceived
scientifically and by humans quite differently. Several
features like loudness ,accent, language are user
dependent , contributes to how the signal is to be
perceived. Emotion recognition is useful in breaching the
gap in human machine interaction.
Recently a lot of work has been done in this area, using
different techniques and features for the same. Several
applications of the emotion recognition system can be
taken into account, such as virtual personal assistants,
automated call centres, automated feedback systems and
other human machine interaction system(HCI) etc.
previously, a lot of graphical methods have been used in
emotion recognition, major work has been done in the
facial emotion recognition system(FER). Also very few
advancements have been made in the speech based
system or the hybrid system.
A lot of literature on different ways to tackle the problem
have been discussed. Features both in time and frequency
domain have been looked into. Few features have found
credible, though as the field is still been explored majority
of the features used are similar to ones used for voice
recognition. As there are a lot of features available to
choose from a few have been discussed in the following
been discussed here.
Automation of this process is contributed majorly by
machine learning and signal processing. One of the most
important parts of the system just like any machine
learning is feature selection. The speech file is just
sequence of sound wave, thus features like amplitude,
frequency, power, etc. There are a lot of features to select
from, in those mel frequency and mel-frequency cepstral
coefficients have proven to be very useful. As both of these
features are designed according to the human frequency
perception.
Thus, most researchers prefer to use combining feature
set that is composed of many kinds of features containing
more emotional information[1]. While that been said, this
increases the data to be processed, which is likely to cause
over fitting and increase time required for result
generation.
The categorization of emotions can be done into many
classes, but so as to keep the problem approachable only
the basic emotions are to be handled. Most popular is the
Ekman model[2], with six emotions. The model used here
has seven emotions classes, enlisted as happy, sad, angry,
scared, surprised, neutral and disgust.
Speech processing has been an area of interest for the last
four decades, but the last decade has witnessed significant
progress in this area of research. This progress has been
possible mainly due to the recent advances made in the
powerful and efficient speech processing techniques such
as vector quantization, hidden Markov Model etc.
In this paper, the first section discussed the introduction
of emotion recognition system. Second section discovered
the speech based emotion emotion recognition system.
Followed by dataset used for analysis and last section
discussed about result and conclusion.
1.1. THE EMOTION RECOGNITION SYSTEM
As Speech based emotion recognition has been in light for
a few years, a lot of innovative methods have been
developed. Even so, basic model has not changed much
over time.

Figure 1: Speech based emotion recognition gives the
fundamental flow of the system.
1. Speech Input
The audio file is to be taken in as input for the system to be
processed. Standard encoding formats like .wav ,.mp3
,ac3, and more for the audio file are expected to be
supported by the system.
Audio Recording is preferred in ‘.wav’ format for
processing and best results. The recording can be from
any device from the system user. If the audio file format is
in other than “.wav”form, then it is converted to “.wav”.
2. Pre-Processing:
The data recording has to be further processed before it
can be worked on. If the features are extracted without
cleaning and pre-processing of the accuracy will be
hampered a lot causing the overall accuracy of the system
to drop very low, and at times generate inconsistent
results. This can also lead to recognition of non existent or
incorrect pattern recognition by the classifier.
This module helps to suppress background noise from the
audio clip to help increase accuracy. At the same time, in
case of multiple speakers, it works out if there are more
than one speaker in the audio clips it separates the data of
the speakers. Silent part of the clips do not contribute to
the final result but increases unnecessary computation,
eliminating the silent parts of audio clip helps reduce the
data to be computed. Further, transformation like, STFT,
log and cosine have been proved to be accuracy boosters.
3. Feature Extraction
Speech emotion feature is the basis for speech emotion
recognition. Extraction accuracy of speech emotion
features in the original speech emotion samples can
influence the final recognition rate of speech emotions
directly.
Feature selection is very important and contributes to
major difference in accuracy of the system. In order to get
maximum accuracy, feature with highest accuracies have
to be extracted and used for processing.
Features like MFCC, contrast, mel frequencies, tonnetz and
chroma have been taken into account
1) MFCC:
Spectral property of voice signals is mostly represented by
Mel-frequency cepstrum coefficient. For each frame, the
Fourier transform and the energy spectrum are estimated
and mapped into the Mel-frequency scale. The discrete
cosine transform (DCT) of the Mel log energies is
estimated.
2) Mel filterbank
The Mel scale relates perceived frequency, or pitch, of a
pure tone to its actual measured frequency. Humans are
much better at discerning small changes in pitch at low
frequencies than they are at high frequencies.
Incorporating this scale makes our features match more
closely what humans hear. [3]
The formula for converting from frequency to Mel scale is:
3) Contrast
contrast is estimated by comparing the mean energy in the
top quantile (peak energy) to that of the bottom quantile
(valley energy).[4]
4) Tonnetz
The Tonal Centroids (or Tonnetz) contain harmonic
content of a given audio signal.
5) Chroma
The entire spectrum is projected onto 12 bins
representing the 12 distinct semitones (or chroma) of the
musical octave.
Once the features are extracted , the values are stored in
file(.csv), for future use.
4. Classification
Model represents the Machine Learning algorithm, many
classifiers are available at hand after so many years of
work in machine learning. Classifier taken in account are
CNN, Random Forest Classifier, Support Vector Machine
and XGBoost.
Speech
Input
Pre
processing
Feature
Extraction
Classification
Databa
se
Decision
Happy
Sad
Angry
Disgust
Neutral
Scared
Surprised

As each classifier has a different way of learning , the
accuracies projected are different. With fine tuning the
classifiers to gain maximum accuracy for each of the
classifiers. Each feature is used as input for the classifiers
and then fine tuned.
Train and testing to be done for models to learn using
different standard datasets. These models once trained is
stored and later it can be loaded, and used to predict the
results.
5. Decision
The output of the system is detected emotion class of the
seven emotions of Angry, happy, sad, neutral, scared,
disgust, and fear.
1.2. DATASET
The dataset used in the experimentation here is SAVEE[5].
Surrey Audio-Visual Expressed Emotion (SAVEE) has a
total of 480 audio sample in .wav format.
The dataset has been recorded by 4 actors (male british),
with 7 emotions used to classify the audio clips. Every
emotion has 15 audio clips for every actor, with the
exception of neutral class with 30 clips. Each clip is of
length ranging from 2 to 3 seconds.
1.3. Implementation
The SAVEE dataset’s file structure is a hierarchy starting
with folder Actor’s name with seven folders for each
emotion, and audio files in those folders. This has been
changed to seven folders one for each emotion with a four
folder one for each actor containing audio clips.
Dataset is in standard format, no background noise is
observed. Even so butterworth filter has been used for
noise elimination and the blank(silent) parts of the clip
are eliminated for performance.
Five features are extracted from the cleaned data for each
audio clip. The features are MFCC, Mel Filter bank(mel),
Contrast, Tonnetz and Chroma. The extracted data is
stored in form of .csv files, for training multiple classifiers,
this saves the time required for feature extraction every
time a classifier is to be trained.
Total of four classifiers are trained and tested on the
dataset on the data namely, Random Forest Classifier,
ConvNet(CNN), XGBoost and SVM.
Convolutional Neural Network is implemented with design
of 5 layer, experiment with the number neuron in each
layer was done. With SVM kernel function is played, all
three kernel functions present in sklearn are
experimented with.
In case Random Forest number of estimators are varied,
and in XGBoost number of estimators, learning rate and
random_state are experimented with. A lot of fine tuning is
done in order to get the most accurate results. Results are
discussed in the next section.
2. RESULTS AND DISCUSSIONS
After the features were extracted from the audio files,
training and testing was done with ratio of 80:20.
In this paper, four different classifiers were used; namely
Convolutional neural network(CNN), Random Forest
classifier(RFC), XGBoost (implementation of gradient
boosting) and Support Vector Machine(SVM).
CNN model was built using KERAS sequential model[6]. In
this 5 layers were used. Activation layers were of relu,
softmax. The layers included 256 neurons in first layer and
128 neurons each in next three layers. Last layer had
seven filters corresponding to seven emotions. Maxpool
was taken to be 4. The number of epochs was decided on
the basis of model loss vs accuracy chart. Initially 1000
epochs were considered, but later changed to 400 epochs
as the model showed the highest accuracy with this count.
Chart-1: Model loss vs epochs with 1000 epochs.
Chart-2: Model loss vs epochs with 400 epochs.

With this model, we got an accuracy of 72.92%, 27.08%,
53.12%, 32.29%, 36.46% for mfcc, tonnetz, mel, chroma
and contrast respectively. MFCC gave the highest accuracy
in CNN model.
For random forest classification[7], entropy criterion was
chosen as it gave better accuracy. The number of
n_estimator had to be changed according to the
GridSearchCV cross validation with cv equal to 10. With
n_estimator values in brackets the accuracies are
67.96(35), 29.16(81), 70.62(675), 38.54(80) and
52.08(70) for mfcc, tonnetz, mel, chroma and contrast
respectively. In this classification technique, mel features
had the highest accuracy.
In XGBoost classifier[8], the accuracies were similar for
features compared to random forest classifier but lesser in
values. The accuracies are 62.5, 21.87, 64.58, 36.45, 48.95
for mfcc, tonnetz, mel, chroma and contrast respectively.
In this classifier also, the mel features had the highest
accuracy. The results for CNN, RFC and XGBoost classifier
is shown in chart-1 and the corresponding accuracy values
in table-1.
Chart-3: Accuracy comparison for CCN, RFC and XG Boost
Table-1: Table for values of accuracy in CCN, RFC and
XGBoost
classifier
feature
MFCC Tonnetz Mel
Filter
bank
Chroma Contrast
CNN 72.92 27.08 65.63 32.29 36.46
RFC 67.96 29.16 70.62 38.54 52.08
XGBoost 62.5 21.87 64.58 36.45 48.95
In Support Vector Machine classifier[9], kernels of linear,
rbf and poly were used taking regularization parameter c
equal to 1. For linear and kernel, mfcc had the highest
accuracy of 68.75%. For rbf kernel, contrast gave the most
accuracy for 49.47% for c=7. Rbf kernel did not show
response to other features. The results for SVM classifier
with linear, rbf and poly kernel is shown in chart-4 and the
corresponding accuracy values in table-2.
Chart-4: Accuracy comparison for SVM classifier using
linear, rbf and poly kernel.
Table-2: Table for values of accuracy in SVM classifier
using linear, rbf and poly kernel.
MFCC Tonnet
z
Mel
Filter
bank
Chrom
a
Contras
t
SVM
kernel=
poly
64.58 27.08 44.79 27.08 41.66
SVM
kernel=
linear
68.75 27.08 33.3 30.2 41.66
SVM
kernel=
rbf
27.08 27.08 28.12 27.08 49.47
3. CONCLUSION
In this paper, multiple emotion recognition features were
presented. This paper presents a comparative analysis of
emotion recognition system using CNN, RFC, XGBoost and
SVM classifier on SAVEE dataset. The emotions were

classified into happy, sad, fear, neutral, angry, disgust and
surprise. CNN model gives the highest accuracy with
72.92% for mfcc features. When trained with Random
Forest Classifier 70.62% accuracy is achieved for mel
features. XGBoost had an accuracy of 64.58% with mel
features and SVMs accuracy was 68.75% for linear model
with mfcc features. It is observed that MFCC and mel
features give highest accuracy and can be used for
emotion recognition depending on the machine learning
model used.
REFERENCES
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