seewave (version 1.6.3)

fdoppler: Doppler effect

Description

This function computes the altered frequency of a moving source due to the Doppler effect.

Usage

fdoppler(f, c = 340, vs, vo = 0, movs = "toward", movo = "toward")

Value

• The altered frequency is returned in a vector.

Details

The altered frequency f' is computed according to: $$f{'} = f\times{\frac{c \pm v_{o}}{c \pm v_{s}}}$$ with f = original frequency produced by the source (in Hz or kHz), vs = speed of the source, vo = speed of the observer.

References

http://www.kettering.edu/~drussell/Demos/doppler/doppler.html.

See Also

wasp

Examples

# a 400 Hz source moving toward or away from the observer at 85 m/s
fdoppler(f=400,vs=85)
# [1] 533.3333
fdoppler(f=400,vs=85,movs="away")
# [1] 320
# use wasp() if you wish to have exact sound speed at a specific temperature
fdoppler(f=wasp(f=400,t=25)$c, vs=85)
# [1] 461.8667
# Doppler effect at different source speeds
f<-seq(1,10,by=1); lf<-length(f)
v<-seq(10,300,by=20); lv<-length(v)
res<-matrix(numeric(lf*lv),ncol=lv)
for(i in 1:lv) res[,i]<-fdoppler(f=f,vs=v[i])
op<-par(bg="lightgrey")
matplot(x=f,y=res,type="l",lty=1,las=1,col= spectro.colors(lv),
xlab="Source frequency (kHz)", ylab="Altered frequency (kHz)")
legend("topleft",legend=paste(as.character(v),"m/s"),
lty=1,col= spectro.colors(lv))
title(main="Doppler effect at different source speeds")
par(op)