## I have started a completely new project - Space Craft Sounds!

Synthesising Bach has been a huge learning curve and very enjoyable indeed, what could possibly follow such a musical experience? Something completely non musical. Music makes an amazing background to work, concentration and relaxation; nevertheless, other sounds can be very effective and maybe less tiring. I remember the sound of a small stream outside on of the houses I lived in as child was very relaxing. A few months ago, my wife and I were travelling across Belgium and I noticed how the throb of the Mercedes V8 and low rumble of the road noise helped her sleep over the motorway sections of our journey.

I have taken these ideas and scaled it up quite a bit! 'Ion Drive' is a super sized version of ambient car/road noise. With a nod to my faithful old Mercedes here is the 'back story':

"

"

So, how was it done? How to make a never repeating sound which whistles and rumbles? The key to the whole effect is in makeEngine. I guess I started off thinking of a regular car engine hence the parameter 'rpm' which give a bass frequency to work with. As I fiddled with ideas (this was an evolution not a design) my imagination got carried away; starting with a few hundred horse power to a few thousand million!

So, the characteristic rumble sound is created not directly from a sine wave but from resonance with the upper harmonics of a distorted sine wave.

I take a sine wave and ring modulate it with a very low frequency sine wave and then distort the result using the Power function. This produces an modulated set of harmonics. The two RBJPeaking filters then resonate at around 10 times the frequency of the initial sine wave. This will produce an unstable set of ringing sounds at around the resonance frequency. An approach like this produces a much more real world, changing and unstable sound than trying to directly create the rumble.

However, this still was not unstable enough. When it comes to engine noise, is seems the more complex the sound the more believable it is; after all, engines are made of a lot of parts, pipe, pannels etc. All these individual things add together to make the real sound and if we do not add enough complexity to the synthesis, it will sound thin and unreal.

So, the next trick was to frequency modulate by a random but very slow signal. This is the thing which give the sound its unstable longitudinal nature.

The rest of the patch is a combination of excitation and convolution reverb. Here is the complete thing.

I have taken these ideas and scaled it up quite a bit! 'Ion Drive' is a super sized version of ambient car/road noise. With a nod to my faithful old Mercedes here is the 'back story':

"

**Ion Drive:***At full power, slight fluctuations in the magnetic ion acceleration coils cause slow, ever changing throbbing to emerge from each bank of huge 1.6 Terra Watt engines. The battle rages outside in the silence of space as this flag ship ‘Europa’ yields burst after burst of withering anti-neutron fire on the retreating force. At these speeds, pulling against Epsilon Major’s gravity, the engines constantly boil off helium coolant which whistles on its super sonic journey to the refrigerator plant. Built on Epsilon IV with engines by Daimler Benz Space Ag and neutron cannons by Advanced Particle Weapons Inc, her prey knows the fight is already lost, no Thor class heavy cruiser has ever been defeated in battle.*

So, how was it done? How to make a never repeating sound which whistles and rumbles? The key to the whole effect is in makeEngine. I guess I started off thinking of a regular car engine hence the parameter 'rpm' which give a bass frequency to work with. As I fiddled with ideas (this was an evolution not a design) my imagination got carried away; starting with a few hundred horse power to a few thousand million!

So, the characteristic rumble sound is created not directly from a sine wave but from resonance with the upper harmonics of a distorted sine wave.

```
sig=sf.SineWave(length,pitch*0.1+random()*0.05)
mod=sf.SineWave(length,0.1+random()*0.05)
mod=sf.DirectMix(1.0,sf.Pcnt50(mod))
sig=sf.Multiply(
sig,
mod
)
sig=sf.Power(sig,10)
sig=sf.RBJPeaking(sig,pitch,1,99)
sig=sf.RBJPeaking(sig,pitch,1,99)
```

I take a sine wave and ring modulate it with a very low frequency sine wave and then distort the result using the Power function. This produces an modulated set of harmonics. The two RBJPeaking filters then resonate at around 10 times the frequency of the initial sine wave. This will produce an unstable set of ringing sounds at around the resonance frequency. An approach like this produces a much more real world, changing and unstable sound than trying to directly create the rumble.

However, this still was not unstable enough. When it comes to engine noise, is seems the more complex the sound the more believable it is; after all, engines are made of a lot of parts, pipe, pannels etc. All these individual things add together to make the real sound and if we do not add enough complexity to the synthesis, it will sound thin and unreal.

So, the next trick was to frequency modulate by a random but very slow signal. This is the thing which give the sound its unstable longitudinal nature.

```
sig=sf.SineWave(length,pitch*0.1+random()*0.05)
mod=sf.WhiteNoise(sLen)
mod=sf.RBJLowPass(mod,8,1.0)
mod=sf.RBJLowPass(mod,8,1.0)
mod=sf.RBJLowPass(mod,8,1.0)
mod=sf.DirectRelength(mod,0.01)
mod=sf.Finalise(mod)
mod=sf.Pcnt50(mod)
mod=sf.DirectMix(1.0,mod)
mod=sf.Pcnt49(mod)
mod=sf.Cut(0,sf.Length(+sig),mod)
print sf.Length(+mod),sf.Length(+sig)
sig=sf.FrequencyModulate(sig,mod)
```

The rest of the patch is a combination of excitation and convolution reverb. Here is the complete thing.

```
sf.SetSampleRate(64000)
from random import random
def excite(sig_,mix,power):
def exciteInner():
sig=sig_
m=sf.Magnitude(+sig)
sigh=sf.BesselHighPass(+sig,500,2)
mh=sf.Magnitude(+sigh)
sigh=sf.Power(sigh,power)
sigh=sf.Clean(sigh)
sigh=sf.BesselHighPass(sigh,1000,2)
nh=sf.Magnitude(+sigh)
sigh=sf.NumericVolume(sigh,mh/nh)
sig=sf.Mix(sf.NumericVolume(sigh,mix),sf.NumericVolume(sig,1.0-mix))
n=sf.Magnitude(+sig)
return sf.Realise(sf.NumericVolume(sig,m/n))
return sf_do(exciteInner)
def reverbInner(signal,convol,grainLength):
def rii():
mag=sf.Magnitude(+signal)
if mag>0:
signal_=sf.Concatenate(signal,sf.Silence(grainLength))
signal_=sf.FrequencyDomain(signal_)
signal_=sf.CrossMultiply(convol,signal_)
signal_=sf.TimeDomain(signal_)
newMag=sf.Magnitude(+signal_)
if newMag>0:
signal_=sf.NumericVolume(signal_,mag/newMag)
# tail out clicks due to amplitude at end of signal
return sf.Realise(signal_)
else:
return sf.Silence(sf.Length(signal_))
else:
-convol
return signal
return sf_do(rii)
def reverberate(signal,convol):
def revi():
grainLength = sf.Length(+convol)
convol_=sf.FrequencyDomain(sf.Concatenate(convol,sf.Silence(grainLength)))
signal_=sf.Concatenate(signal,sf.Silence(grainLength))
out=[]
for grain in sf.Granulate(signal_,grainLength):
(signal_i,at)=grain
out.append((reverbInner(signal_i,+convol_,grainLength),at))
-convol_
return sf.Clean(sf.FixSize(sf.MixAt(out)))
return sf_do(revi)
def makeEngine(length_,rpm):
def inner():
pitch=2.0*float(rpm)/60.0
length=float(length_)
sig=sf.SineWave(length,pitch*0.1+random()*0.05)
mod=sf.SineWave(length,0.1+random()*0.05)
mod=sf.DirectMix(1.0,sf.Pcnt50(mod))
sig=sf.Multiply(
sig,
mod
)
sig=sf.Power(sig,10)
sig=sf.RBJPeaking(sig,pitch,1,99)
sig=sf.RBJPeaking(sig,pitch,1,99)
sig=sf.Finalise(sig)
noise=sf.WhiteNoise(length)
noise=sf.Power(noise,5)
noise=sf.FixSize(noise)
noise=sf.ButterworthLowPass(noise,32,2)
noise=sf.Finalise(noise)
sig=sf.Mix(
sf.Pcnt98(sig),
sf.Pcnt2(noise)
)
sig=sf.Finalise(sig)
sig2=sf.RBJPeaking(+sig,pitch*32,4,99)
sig=sf.Mix(
sf.Pcnt10(sf.FixSize(sig2)),
sig
)
sig=sf.Cut(1,sf.Length(+sig)-1,sig)
sLen=sf.Length(+sig)*0.011
mod=sf.WhiteNoise(sLen)
mod=sf.RBJLowPass(mod,8,1.0)
mod=sf.RBJLowPass(mod,8,1.0)
mod=sf.RBJLowPass(mod,8,1.0)
mod=sf.DirectRelength(mod,0.01)
mod=sf.Finalise(mod)
mod=sf.Pcnt50(mod)
mod=sf.DirectMix(1.0,mod)
mod=sf.Pcnt49(mod)
mod=sf.Cut(0,sf.Length(+sig),mod)
print sf.Length(+mod),sf.Length(+sig)
sig=sf.FrequencyModulate(sig,mod)
return sf.Realise(sig)
return sf_do(inner)
length = 60*60000
chans = 16
rpm = 2200
sigs = []
for x in range(0,chans):
l=float(x)/float(chans)
r=1.0-l
sig=makeEngine(length,rpm)
sigs.append(((l,r),sig))
def mix(sigs,pos,keep=True):
def inner():
toMix=[]
for lr,sig in sigs:
v=lr[pos]
if keep:
+sig
p=30.0*v
toMix.append((sf.NumericVolume(sig,v),p))
sig=sf.Realise(sf.Finalise(sf.MixAt(toMix)))
sig=sf.Power(sig,1.1)
sig=sf.Cut(1,sf.Length(+sig)-1,sig)
return sf.Finalise(sig)
return sf_do(inner)
left = mix(sigs,0)
right = mix(sigs,1,False)
print "Entering reverb"
(convoll,convolr)=sf.ReadFile("temp/bh-l.wav")
(convorl,convorr)=sf.ReadFile("temp/bh-r.wav")
convoll=excite(convoll,0.75,2.0)
convolr=excite(convolr,0.75,2.0)
convorl=excite(convorl,0.75,2.0)
convorr=excite(convorr,0.75,2.0)
ll = reverberate(+left ,convoll)
lr = reverberate(+left ,convolr)
rl = reverberate(+right,convorl)
rr = reverberate(+right,convorr)
wleft =sf.FixSize(sf.Mix(ll,rl))
wright=sf.FixSize(sf.Mix(rr,lr))
wright = excite(wright,0.15,1.11)
wleft = excite(wleft ,0.15,1.11)
right = excite(right,0.15,1.05)
left = excite(left ,0.15,1.05)
wleft =sf.FixSize(sf.Mix(sf.Pcnt15(left),sf.Pcnt85(wleft)))
wright =sf.FixSize(sf.Mix(sf.Pcnt15(right),sf.Pcnt85(wright)))
sf.WriteFile32((wleft,wright),"temp/mix.wav")
```