function replace(string,alt,neu) {
	var pos=string.indexOf(alt);
	if (pos == -1) return string;
	string = string.substring(0,pos)+neu+string.substring(pos+1,string.length);
	return string;
}

function validate(string){
	if(isNaN(string)) alert(string+" ist keine gültige Zahl!");
	return string;
}

function schalldruck() {
	var lw = validate(replace(document.getElementsByName("lw")[0].value,",","."));
	var l = validate(replace(document.getElementsByName("l")[0].value,",","."));
	var b = validate(replace(document.getElementsByName("b")[0].value,",","."));
	var h = validate(replace(document.getElementsByName("h")[0].value,",","."));
	var x = validate(replace(document.getElementsByName("x")[0].value,",","."));

	var sx = (2*x + l*1)*(2*x + b*1)+(x*1+h*1)*2*(4*x + l*1 + b*1);
	var lp = lw-10*Math.log(sx)/Math.log(10);
	var lp = Math.round(lp*100)/100;

	document.getElementsByName("lp")[0].value = lp;
}

function energiekosten() {
	var kla = validate(replace(document.getElementsByName("kla")[0].value,",","."));
	var klb = validate(replace(document.getElementsByName("klb")[0].value,",","."));
	var laa = validate(replace(document.getElementsByName("laa")[0].value,",","."));
	var lab = validate(replace(document.getElementsByName("lab")[0].value,",","."));
	var euro = validate(replace(document.getElementsByName("euro")[0].value,",","."));
	var haa = validate(replace(document.getElementsByName("haa")[0].value,",","."));

	var hab = (haa*kla)/klb;
	var eka = (laa/1000)*haa*(euro/100);
	var ekb = (lab/1000)*hab*(euro/100);
	var eera = kla/laa;
	var eerb = klb/lab;
	var diff = eka*1-ekb*1;

	if (eera <= 2.2) {var eefa = "G";}
	else if (eera < 2.4) {var eefa = "F";}
	else if (eera < 2.6) {var eefa = "E";}
	else if (eera < 2.8) {var eefa = "D";}
	else if (eera < 3.0) {var eefa = "C";}
	else if (eera <= 3.2) {var eefa = "B";}
	else if (eera > 3.2) {var eefa = "A";}
	else {alert("Berechnungsfehler");}

	if (eerb <= 2.2) {var eefb = "G";}
	else if (eerb < 2.4) {var eefb = "F";}
	else if (eerb < 2.6) {var eefb = "E";}
	else if (eerb < 2.8) {var eefb = "D";}
	else if (eerb < 3.0) {var eefb = "C";}
	else if (eerb <= 3.2) {var eefb = "B";}
	else if (eerb > 3.2) {var eefb = "A";}
	else {alert("Berechnungsfehler");}

	document.getElementsByName("hab")[0].value = Math.round(hab);
	document.getElementsByName("eka")[0].value = Math.round(eka*100)/100;
	document.getElementsByName("ekb")[0].value = Math.round(ekb*100)/100;
	document.getElementsByName("eera")[0].value = Math.round(eera*100)/100;
	document.getElementsByName("eerb")[0].value = Math.round(eerb*100)/100;
	document.getElementsByName("diff")[0].value = Math.round(diff*100)/100;
	document.getElementsByName("eefa")[0].value = eefa;
	document.getElementsByName("eefb")[0].value = eefb;
}