How to disable audio option

Hi, The audio captcha is only English.For a not English website with not English speaking users this is annoying.I need to disable this option, and only allow the image captcha. Since the reCaptcha is an iframe I can't just hide the button. How could I disable the audio captcha? Regards,  Jonathan. -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.