Damage may be a result of the direct effects of alcohol on the brain or may result indirectly, from a poor general health status or from severe liver disease. For example, thiamine deficiency is a common occurrence in people with alcoholism and results from poor overall nutrition.
In the case of a longitudinal wave, a wavelength measurement is made by measuring the distance from a compression to the next compression or from a rarefaction to the next rarefaction. On the diagram above, the distance from point A to point C or from point B to point D would be representative of the wavelength.
Here is an example of longitudinal chromatic aberration that is visible at different distances: NIKON D3S + 35mm f/1.4 @ 35mm, ISO 200, 1/320, f/1.4. Note the green color on the top of the image, transforming to neutral in the middle, then becoming purple on the bottom part of the image that is closer to the camera.