Digital Signal Processing Reference
In-Depth Information
5
6
4
0
1000 Hz
2
-5
0
0
0.005
0.01
0
2000
4000
6000
8000
Time (sec.)
Frequency (Hz)
10
6
5
1000 Hz
4
0
3000 Hz
2
-5
-10
0
0
0.005
0.01
0
2000
4000
6000
8000
Time (sec.)
Frequency (Hz)
FIGURE 1.5
Audio signals and their spectrums.
1.3
OVERVIEW OF TYPICAL DIGITAL SIGNAL PROCESSING IN REAL-WORLD
APPLICATIONS
1.3.1
Digital Crossover Audio System
An audio system is required to operate in an entire audible range of frequencies, which may be beyond
the capability of any single speaker driver. Several drivers, such as the speaker cones and horns, each
covering a different frequency range, are used to cover the full audio frequency range.
Figure 1.7
shows a typical two-band digital crossover system consisting of two speaker drivers:
a woofer and a tweeter. The woofer responds to low frequencies, while the tweeter responds to high
frequencies. The incoming digital audio signal is split into two bands by using a digital lowpass filter
and a digital highpass filter in parallel. Then the separated audio signals are amplified. Finally, they are
sent to their corresponding speaker drivers. Although the traditional crossover systems are designed
using the analog circuits, the digital crossover system offers a cost-effective solution with program-
mability, flexibility, and high quality. This topic is taken up in Chapter 7.
1.3.2
Interference Cancellation in Electrocardiography
In ECG recording, there often is unwanted 60-Hz interference in the recorded data (Webster, 1998).
The analysis shows that the interference comes from the power line and includes magnetic induction,
Search WWH ::
Custom Search