Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Direct quantitative measurements of Doppler effects for sound sources
  with gravitational acceleration
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn