We can probe this matter a little more in-depth. This introductory reference describes all the giant or Jovian planets, noting that only the two more massive ones, Jupiter and Saturn, are made primarily of hydrogen and helium. Uranus and Neptune, which did not have as much material to work with and did not become powerful enough to draw large proportions ...
A good example is the Fourier imaging asteroseismology technique used by SYMPA:
SYMPA, a dedicated instrument for Jovian seismology I. Principle and performance
SYMPA, a dedicated instrument for Jovian seismology
II. Real performance and first results
Detection of Jovian seismic waves: a new probe of its interior structure
JOVIAL is next-gen implementation,...