# 1D Sound Wave
This test initializes a compression/rarefaction wave across the grid. The setup consists of an initial density and pressure of 1.0 and 0.6, respectively. A sound wave is initialized as a sinusoidal wave with amplitude 1e-4 and wavelength of 1.0. Gamma is set to 1.666666666666667. This test was performed with the hydro build (`cholla/builds/make.type.hydro`) and Van Leer integrator. Full initial conditions can be found in `cholla/src/grid/initial_conditions.cpp`under `Sound_Wave()`. 

The parameter file can be found at: {repository-file}`examples/1D/sound_wave.txt`

## Parameter file:
```
#
# Parameter File for sound wave test
#

################################################
# number of grid cells in the x dimension
nx=128
# number of grid cells in the y dimension
ny=1
# number of grid cells in the z dimension
nz=1
# final output time
tout=0.05
# time interval for output
outstep=0.01
# name of initial conditions
init=Sound_Wave
# size of domain
xmin=0.0
ymin=0.0
zmin=0.0
xlen=1.0
ylen=1.0
zlen=1.0
# type of boundary conditions
xl_bcnd=1
xu_bcnd=1
yl_bcnd=0
yu_bcnd=0
zl_bcnd=0
zu_bcnd=0
# path to output directory
outdir=./sowvout

#################################################
# Parameters for linear wave problems
# initial density
rho=1.0
# velocity in the x direction
vx=0
# velocity in the y direction
vy=0
# velocity in the z direction
vz=0
# initial pressure
P=0.6
# amplitude of perturbing oscillations
A=1e-4
# value of gamma
gamma=1.666666666666667

```
Upon completion, you should obtain five output files. By changing the outstep to 1, we can obtain the evolution of the density, pressure, and velocity.  Examples of how to extract and plot data can be found in the [General 1D Plotting Example](../../PythonExamples/1D-plotting.md).  

:::{video} new_soundwave_2.mp4
    :width: 700
    :height: 500
    :align: center
    :autoplay:
    :loop:
:::