Chapter 2 Communication and Internet Technologies

Sample rate

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

• The sample rate is how many samples, or measurements, of the sound are taken each second.
• The more samples that are taken, the more detail about where the waves rise and fall is recorded and the higher the quality of the audio. Also, the shape of the sound wave is captured more accurately.

Sample rate

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

• Sound is recorded at set timed intervals; this process is known as sampling

Sample rate

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

Task: Create a sound wave

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

• Using the table below create a sound wave.

Time samples	1	2	3	4	5	6	7	8	9	10	11	12
Sound values	5	4	9	15	13	9	1.5	9	3.5	9	8	5.5

Sample rate

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

• Sample rates are measured in hertz.
• 1 hertz = 1 sample in 1 second
• Telephone samples a voice at 8000Hz
• CD samples music at 44100Hz

Sample rate

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

Advantages:
More accurately reflects true sound wave
Higher Sampling rate
Disadvantages:
More data, bigger file
44,100 Hz is the norm for CD quality

ADC and DAC

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

• Analog-to-digital converters, abbreviated as “ADCs,” work to convert analog (continuous, infinitely variable) signals to digital (discrete-time, discrete-amplitude) signals.
• A DAC (Digital-to-analog converter) takes digital data and transforms it into an analog audio signal. Afterward, it sends that analog signal to an amplifier.

Bit depth

OBJECTIVES:

• Show understanding that sound (music), pictures, video, text and numbers are stored in different formats

• Bit depth is the number of bits available for each sample.
• The higher the bit depth, the higher the quality of the audio.
• Bit depth is usually 16 bits on a CD and 24 bits on a DVD.
• A bit depth of 16 has a resolution of 65,536 possible values (ranging from 0 to 65,535).
• A bit depth of 24 has over 16 million possible values (ranging from 0 to 16,777, 216).