Low Sensor Output Frequency with multiple sensors

Using Arduino Sensors
1 
  duration1 = pulseIn(echoPin1, HIGH);
  duration2 = pulseIn(echoPin2, HIGH);
  duration3 = pulseIn(echoPin3, HIGH);
  durationp = pulseIn(echoPinPedal, HIGH);

I'm running multiple ultrasonic sensors on one Arduino Uno, and I notice the frequency of sensor readings going down dramatically having multiple sensors in line like this. If I comment out three of the four sensors the speed goes up significantly, but I need all my sensors working.

Any ideas on how I can make sure this problem is gone? I can't work my code properly if it's only giving readings once every two seconds.

2

Annoyingly, it also seems that my other sensors aren't measuring at all if others are active.

3

Shorten the timeout.

4

AWOL:
Shorten the timeout.

How do I do that? And are there any risks to it?

5

Start with the reference manual page.

Decide if pulseIn is really a sensible thing to do in your situation, paying particular attention to the fact that pulseIn is blocking.

6

Are the sensors located near each other? With two (or more) sensors side-by-side, the second sensor may detect a late echo from the first one (the back wall, for instance) and it's a pretty dumb sensor: it will think that it's hearing its own ping and it will give you a result that's too small or wildly inconsistent.

Make sure the timeout on pulseIn() is set to something just slightly longer than the longest value you expect to measure. Then add extra delays if the sensors are likely to receive long echoes from earlier sensors.