• Definition• Periodic variation in air pressure

• As we speak, vibrations created by our vocal cords travel in the medium of air

• These vibrations travel through the air and cause sound wave just like a boat moving through water causes waves in the water

Sound and Electrical Waves

Wave in either air or water emanating from a source

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• Distinguishing Characteristics • Frequency

• Definition: • Number of occurrences during a specific period of time• Examples: Frequency of the seasons, full moons, etc.

• As used in Communications• Used to distinguish between the different sounds wave of that

sound will occur in one second • The period of a wave is the length of time required for one

wave

Sound and Electrical Waves

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Five cps analog waveform

• Distinguishing Characteristics • Frequency

Sound and Electrical Waves

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• Distinguishing Characteristics • Wavelength

• In sound the standard unit of time is a second• Definition

• The physical length of one waveform

Sound and Electrical Waves

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• Distinguishing Characteristics • Amplitude

• Term used to describe the strength of a signal

Sound and Electrical Waves

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Voltage is used to measure the signal strength of various amplitudes. The greater the amplitude, the louder the sound and the stronger the signal.

• Frequencies Peoples use in Communications• The full range of frequencies that can be heard is 20 –

20kHz• Most of the information in human speech can be

represented with 300 – 4000 Hz• Telephones use this smaller range as a historical compromise

that balances the information content with reliable transmission distance

• Compromised developed during the late 1800’s and early 1900’s

• Sound Waves verses Electrical Waves• Within the frequency limitations of the telephone

• The sound waves and resulting electrical wave track• They have different speeds

Sound and Electrical Waves

• Sound Waves verses Electrical Waves• Within the frequency limitations of the telephone

• The sound waves and resulting electrical wave track• Different wavelengths due to the different speed

» 250 Hz sound wave travels through the air at 331.5 m/s and has a wavelength of 1.326 meters

» A 250 Hz analog electrical signal leaveing a telephone on a pair of wires has a wavelength of 3x108m/ 250 = 1.2 x 106m

• However both still have the same frequency and period» 250 cycles per second or 250Hz» And each cycle takes 0.004 seconds to complete

Sound and Electrical Waves