Audio Engineering

438 Chapter 15

When we attempt to take a measurement from this plot we will need to recognize the
effects of limited measurement accuracy and resolution. As we attempt greater resolution
we will fi nd that we approach a limit described by the noise or random errors in the
measurement technique. You should appreciate the difference between resolution and
accuracy since inaccuracy gives rise to distortion in the measurement due to some
nonlinearity in the measurement process. This facility of measurement is useful. Suppose,
for example, that we wished to send the information regarding the tidal heights we had
measured to a colleague in another part of the country. One, admittedly crude, method
might involve turning the drum as we traced out the plotted shape while at the far end an

4.0

3.6

3.2

2.8

2.4

2.0

1.6

1.2

0.8

0.4

 6  5  4  3  2  1  1  2  3  4  5

High water

Hours after high water

Spring tide

Height (m)

Figure 15.1 : The plot of tidal height versus diurnal time for Portsmouth, United Kingdom,

time in hours. Mariners will note the characteristically distorted shape of the tidal curve

for the Solent. We could mark the height as a continuous function of time using the crude

arrangement shown.