Every earlier resolution lesson in this book fixed sound speed at 12 m/s and only ever scanned frequency (chapter five) or cycle count (chapter six). This scan holds frequency (3 Hz) and cycle count (2) fixed and checks three sound speeds instead: 6 m/s gives wavelength 2 m and axial limit 2 m, 12 m/s reproduces every earlier lesson's own checked sound speed exactly at wavelength 4 m and limit 4 m, and 18 m/s gives wavelength 6 m and limit 6 m. Sound speed is not a fixed background constant; it sets the wavelength before frequency or cycle count are ever applied.
Sound speed itself sets wavelength before frequency or cycle count are ever applied. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Every earlier resolution row held sound speed fixed at twelve
Every earlier resolution lesson in this book kept sound speed at 12 metres per second and only ever varied frequency or cycle count. Here frequency stays fixed and cycle count stays fixed; sound speed itself is the source factor that rescales the checked wavelength.
λ=fc,Δd=2Nλ
Three sound speeds give three exact wavelength budgets
The frequency and cycle count never change across these rows. Sound speed alone rescales wavelength, pulse length, and the axial resolution limit together.
c61218f333λ246Δd246
The middle row is the book's own checked twelve-meter speed
The final display follows the same checked wavelength and cycle count as the diagram; sound speed is the only factor this scan changes.