PALESTINE POLYTECHNIC UNIVERSITY
COLLEGE OF ADMINISTRATIVE SCIENCES AND INFORMATICS
MULTIMEDIA AND GRAPHIC DEPARTMENT
4737– Computer Modeling (‫)المحوسبة النماذج‬
First Exam
Eng. Abdalfatah Najjar
[email protected]
First Semester 2013-2014
Student name:…………………………………………...…
Date: Tuesday, April 1, 2014
Student number: ……………………………………….….
Time duration: 60 min.
NOTES:
Please read these instructions carefully before you start.
Exam Rules:
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‫اكتب اسمك الثالثي باللغة العربية‬
The duration of the exam is strictly 60 minutes. No extra time will be given
This exam is closed book and closed notes.
No books, notes, calculators, cellular phones, PDAs, or other electronic devices are permitted.
You must write clearly! Answers which are illegible will receive no credit.
Hints:
 Do not complete the questions in this exam in the order they appear. First, read through the entire exam.
Then, prioritize each question according to how well you know it and how many points it are worth.
 Work quickly and efficiently.
 You don't have to fill all the space that is given.
 Please use a pen for all answers.
Any CHEATING will result in an F as well as being written-up on academic dishonesty.
ATTENTION: Make sure your exam has 5 pages and all 3 questions.
Question #
Q1
Q2
Q3
Total Grade
Points Available
10
20
10
40
Points Earned
You got
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out of 20 points.
[Question#1] Tough Choices (10 points)
For each of the following questions, circle one answer out of the choices given.
1.
Which of the following binary codes CANNOT be a Huffman code for any distribution? (2 points)
A. 0, 10, 111, 101
B. 00, 010, 011, 10, 110
C. 1, 000, 001, 010, 011
(According
2.
to the Unique prefix property)
MIDI data is different than audio data because :
A. it is the audio that comes from a MIDI keyboard
B. it is highly compressed audio data and is smaller
C. because it contains instructions for sequencers when to play notes, change programs, and turn knobs
D. You guys are dumb, MIDI is Audio!
E. B and C are true
(Remember that MIDI is only made up of instructions for devices to play sounds--not sounds themselves)
3.
4.
The human ear can respond to minute pressure variations in the air if they are in the audible frequency
range, roughly__________________.
A. 20 Hz - 20 kHz.
B. 20 mHz - 200 kHz.
C. 200 Hz - 20 kHz.
D. 20 Hz - 200Hz.
Sound A is a tone played at 1000 Hz, sound B is played at 2000Hz, sound C is played at 10kHz, sound D
is played at 11kHz. All are played at 60DB SPL. Which sounds like a greater increase in pitch? (2
points)
A. The increase from Sound A to Sound B.
B. The increase from Sound C to Sound D.
C. They pitch increase from Sound A to Sound B is perceived as the same as the pitch increase from
Sound C to Sound D.
5.
Sound A is a tone played with 200,000 μPa, sound B is played at 300,000 μPa, sound C is played at
1,000,000 μPa, sound D is played at 1,100,000 μPa. All are played at 2000 Hz. Which sounds like a
greater increase in loudness? (2 points)
A. The increase from Sound A to Sound B.
B. The increase from Sound C to Sound D.
C. The loudness increase from Sound A to Sound B is perceived about the same as the loudness increase
from Sound C to Sound D.
6.
Sound A is a tone played with 30 DB SPL, sound B is played at 35 DB SPL, sound C is played at 80 DB
SPL, sound D is played at 85 DB SPL. All are played at 2000 Hz. Which sounds like a greater increase
in loudness? (2 points)
A. The increase from Sound A to Sound B.
B. The increase from Sound C to Sound D.
C. The loudness increase from Sound A to Sound B is perceived about the same as the loudness
increase from Sound C to Sound D.
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[Question#2] (20 points)
A. For the following set of symbols (10 points)
symbol
A1
A2
A3
A4
probability
0.4
0.2
0.3
0.1
a) What is the entropy?
b) Design a Huffman code for these symbols to be compressed?
c) What is the average word length?
d) What is the efficiency?
B.
We wish to develop a new Internet service, for doctors. Medical ultrasound is in the range 2-10 MHz; what
should our sampling rate be chosen as? Why? (2 points)
‫حسب نظرية نيكوست‬
2*10 = 20 MHz
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C. Calculate the entropy of a “checkerboard” image in which half of the pixels are BLACK and half of
them are WHITE. (5 points)
1 bit/symbol.
D. The graph below show a complex wave forms. Refer to this graph when answering questions below: (3
points)
What are the amplitude, frequency and sound level of the complex waveforms?
a) Amplitude 2 N/m2
b) Frequency 250
Hz
3 cycles ----------------12*10-3sec
???----------------------1 sec
c)
Level
100 dB
dB SPL =20*log (2/0.00002) = 20*5 =100
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[Question#3] (10 points)
Figure 1 shows two simple periodic waves labeled “A” and “B” and a periodic complex wave which is their
sum “A+B”.
Figure 1: simple waves “A” and “B” and their sum “A+B”.
a) What is the frequency (in Hz) of sine wave A?
600Hz.
There are 3 cycles in 5 milliseconds. How many cycles are in 1 second?
b) What is the frequency (in Hz) of sine wave B?
800 Hz.
There are 4 cycles in 5 milliseconds. How many cycles in1,000 milliseconds?
c) What is the amplitude of sine wave A?
1.5
d) What is the amplitude of sine wave B?
0.5
e) What is the fundamental frequency of the complex wave A+B?
200 Hz.
The fundamental frequency is the greatest common denominator (GCD) of the frequencies of the
component waves. The GCD of of 600 and 800 is 200 because no larger number evenly divides
both 600 and 800.
Good luck
Course instructors: Eng.Abdalfatah Najjar
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