Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Echo-based measurement of the speed of sound   The speed of sound in air can be measured by popping a balloon next to a
microphone a measured distance away from a large flat wall, digitizing the
sound waveform, and measuring the time between the sound of popping and return
of the echo to the microphone. The round trip distance divided by the time is
the speed of sound.

4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas