Doppler effect
This function computes the altered frequency of a moving source due to the Doppler effect.
fdoppler(f, c = 340, vs, vo = 0, movs = "toward", movo = "toward")
f |
original frequency produced by the source (in Hz or kHz) |
c |
speed of sound in meters/second. |
vs |
speed of the source in meters/second. |
vo |
speed of the observer in meters/second. The observer is static by default
i.e. |
movs |
movement direction of the source in relation with observer position,
either |
movo |
movement direction of the observer in relation with the source position,
either |
The altered frequency f' is computed according to:
f' = f*(c+/-vo/(c+/-vs))
with f = original frequency produced by the source (in Hz or kHz),
vs = speed of the source,
vo = speed of the observer.
The altered frequency is returned in a vector.
You can use wasp to have exact values of c.
See examples.
Jerome Sueur sueur@mnhn.fr
# 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)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.