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an introduction to sound
Different types of sounds have different types of waves but fundamentaly they all have the same shape. In previous lessons we have found out how a computer can use binary to store numbers, text and images. Today we will find out how a computer can store sound using 0 and 1.
When an object, an instrument or a person vibrates (especially by speaking) it changes the surrounding air pressure and creates a series of waves, which the brain interprets as sounds.
Sound Waves
This is an electrical representation of a sound wave known as an analog signal. The parts of the analog signal are shown here. It is not critical to know all the parts of the analog signal, but it is important to realize that these waveforms are converted into a digital format of 1's and 0's.
Analog Signal
When an object, an instrument or a person vibrates (especially by speaking) it changes the surrounding air pressure and creates a series of waves, which the brain interprets as sounds.
Sound Waves
This is an electrical representation of a sound wave known as an analog signal. The parts of the analog signal are shown here. It is not critical to know all the parts of the analog signal, but it is important to realize that these waveforms are converted into a digital format of 1's and 0's.
Analog Signal
Analog
All waves have three characteristics, amplitude (strength), frequency, and phase. Variations, called modulations, in wave characteristics are used to encode analog signals to digital signals. Analog signals are continuous signals that vary in strength. Amplitude is the height of the wave at any point in relation to the zero line. |
Telephones have transmitters that encode sound waves into electrmagnetic waves, which then travel over wires to their destination. The receiving telephone decodes the electromagnatic waves back into sound waves
Our brains then decode the sound waves into the words we hear. Computer modems use the same principle.
Analog signals can be represented digitally. For instance, a high electromagnetic voltage could be interpreted as 1 and low voltage as 0.
Activity 1
Open Power Point and put "An Introduction to Sound" as your title slide. On the next slide explain using text and images what a sound wave is and include some of the characteristics. Save your work into your IT folder and keep it open.
Our brains then decode the sound waves into the words we hear. Computer modems use the same principle.
Analog signals can be represented digitally. For instance, a high electromagnetic voltage could be interpreted as 1 and low voltage as 0.
Activity 1
Open Power Point and put "An Introduction to Sound" as your title slide. On the next slide explain using text and images what a sound wave is and include some of the characteristics. Save your work into your IT folder and keep it open.
Taking Measurements
A converter within the sound card of the computer takes readings each second. These readings are positions (voltages, actually) on the wave in relation to the zero line. They are recorded and then converted from decimal to binary numbers. Once they are converted, the waveforms can be transformed into one of several audio formats such as WAV (file extension .wav) or AU (file extension au). |
Sampling
This process of measuring and recording the signal and voltage is called "Sampling". The time between measurments being taken is call the "Sampling rate". The more often a reading is taken will determine the quality of the sound being reproduced.
In order for a CD quality recording to be made, the analog signal must be read approximately 44,000 times a second. That is a hugh amount of binary information but if the sampling rate drops below this level, the human ear detects distortions in the recording.
Activity 2
Go back to your power point and on a new slide explain how the computer converts a sound into binary. Include a comment about how the quality of the sound may be affected.
This process of measuring and recording the signal and voltage is called "Sampling". The time between measurments being taken is call the "Sampling rate". The more often a reading is taken will determine the quality of the sound being reproduced.
In order for a CD quality recording to be made, the analog signal must be read approximately 44,000 times a second. That is a hugh amount of binary information but if the sampling rate drops below this level, the human ear detects distortions in the recording.
Activity 2
Go back to your power point and on a new slide explain how the computer converts a sound into binary. Include a comment about how the quality of the sound may be affected.
Digital Signals
Digital signals are discrete rather than continuous. Either there is a signal or there isn't a signal. Telegraphs transmit data with discrete signals. You either hear a tap or you do not hear a tap. Discrete signals can be represented by on and off pulses. The duration of a discrete signal can be varied, as with dots and dashes in Morse Code.
Digital signals are discrete rather than continuous. Either there is a signal or there isn't a signal. Telegraphs transmit data with discrete signals. You either hear a tap or you do not hear a tap. Discrete signals can be represented by on and off pulses. The duration of a discrete signal can be varied, as with dots and dashes in Morse Code.
Discrete signals can also be represented digitally. The presence of a signal could be coded as a 1 and the absence of a signal coded as a 0. The computer’s brain,the central processing unit (CPU), transforms these codes of 0s and 1s into
the voice, video and data we see.
Activity 3
Go back to your power point and explain what is meant by a "Digital signal" and how the computer stores it. Save and print your power point 2 slides to a page.
the voice, video and data we see.
Activity 3
Go back to your power point and explain what is meant by a "Digital signal" and how the computer stores it. Save and print your power point 2 slides to a page.
Extended Activities
Use the internet to find out what the abbreviations ADC and DAC stand for Write up a learning Blog about todays lesson. Tell me what do know now that you didn't know before this lesson? |