## 2pPAb12. Comparison of sound-speed computation methods.

### Session: Tuesday Afternoon, May 14

### Time: 4:15

**Author: George S. K. Wong**

**Location: Inst. for Natl. Measurement Standards, National Res. Council, Ottawa, ON K1A 0R6, Canada**

**Abstract:**

The computation of sound speeds in nitrogen, oxygen, and methane was
performed with two methods. Results from the traditional method that relied on
virial coefficients B and their temperature derivatives T dB/dT, T[sup 2] d[sup
2]B/dT[sup 2], were compared with those given by a simplified method. At a
pressure of 101.325 kPa, and at a temperature of -10 (degrees)C, the maximum
sound speed deviations between the two methods are within 0.2% and -0.4% for
nitrogen and oxygen, respectively. For methane, at the above pressure, and over
the temperature range from zero to 450 (degrees)C, the maximum deviation is
1.2%. For the above gases, the sound-speed deviations between the methods are
largest at low temperatures. It can be shown that by modifying the numerical
values of the virial coefficients and their temperature derivatives, the
sound-speed deviations between the two methods can be reduced substantially. For
nitrogen, when B, T dB/dT, and T[sup 2] d[sup 2]B/dT[sup 2] are modified by
multiplication factors of -0.1, 0.55, and 0.7, respectively, the difference
between the sound speeds obtained with the two methods decreases to less than
(plus or minus)0.05%. It is noted that the sign of the numerical value of B is
reversed. Uncertainties of the results obtained with both methods were examined.

from ASA 131st Meeting, Indianapolis, May 1996