Only get returns of 328 cm with PING))

:question I've tried using the example code and only get returns of 328cm. Then I tried simplifying it, trying to understand whats going on but with little success.

// Simplified Ping Code

const int pingPin = 7; int duration;

void setup() { Serial.begin(9600); }

void loop() { pinMode(pingPin, OUTPUT); digitalWrite(pingPin, LOW); delayMicroseconds(2); digitalWrite(pingPin, HIGH); delayMicroseconds(5); digitalWrite(pingPin, LOW); pinMode(pingPin, INPUT); duration = pulseIn(pingPin, HIGH, 700); Serial.println(duration); delay(500); }

In the Serial Monitor I get returns of ... 19088 19088 19089 19088

I've tried different pins and I'm using a book as a target with the Ping)) on the edge of a table.