Please explain what a negative sound level, such as -10 db, is.Objectives are to (1)demonstrate the properties that sound shares with other waves,...

The decibel is by definition a dimensionless logarithmic
quantity from a the intensity of sound reported to a standard reference
intensity.

`dB =10*log(I/I_0)` 

where `I_0 =10^-12 W/m^2`

The reference intensity is taken as the lowest sound
intensity that in normal conditions is audible. Lower sound intensity levels than the
reference intensity are usually inaudible.

The
corresponding sound intensity for a -10 dB level is

`-10
=10*log(I/I_0)`

`-1 =log(I/I_0)`

`I =I_0*10^-1 =10^-12*10^-1 =10^-13 W/m^2`

Sound is just an oscillation of the air molecules and thus
it is transmitted over large distances like a wave. The decibel scale was invented as a
necessity to measure oscillations intensities spread over a very wide range (for example
the highest audio sound intensity when all the air in one semi-plane of the oscillation
is depleted, is about `10^20`  ` ` times the lowest audible sound). The human perception
of sound (the ear) is working in a range of intensities of about `10^14`
.