# Re: Headphone sound pressure level?

Dear Gemma.

I don't know about that IEC standard but 113 dB/V is the sensitivity of the device and that is not a maximum pressure level. Maximum level can be estimated from sensitivity, power handling and impedance as power is: W=V^2/Z

 Nominal impedance 64 Ohm Sound pressure level (SPL) 102 dB (IEC 268-7) Load rating 500 mW
Maximum rms voltage is Vmax=SQRT(0,5·64)=5,6 V
So maximum SPL should be 113+20 log(5,6)= 128 dB

Now you have two solutions: 102 dB under IEC-268 and 128 dB when loaded with 500 mW, obviously there's a huge difference so I recommend you to just measure the SPL under the closer conditions you'll have on your tests.

Best regards. Jose.

2011/7/13 Gemma Rachael Hutchinson
Dear all,

We have a set of Sennheiser HD 280 pro headphones with a "sound pressure level" of 102 dB "as per IEC 268-7". Since it also states a sound pressure level of 113dB/1V rms, we are unsure exactly what the maximum output level of these headphones actually is. The impedance is 64ohm. Would anyone know how to calculate this, or does anyone have access to the full international standard for headphones (e.g., IEC 60268-7), a preview of which can be found at the link below?

http://webstore.iec.ch/preview/info_iec60268-7%7Bed3.0%7Den.pdf

Thanks, Gemma