From owner-freebsd-current@FreeBSD.ORG Wed Sep 19 18:06:20 2012 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 89270106566C; Wed, 19 Sep 2012 18:06:20 +0000 (UTC) (envelope-from kaduk@mit.edu) Received: from dmz-mailsec-scanner-1.mit.edu (DMZ-MAILSEC-SCANNER-1.MIT.EDU [18.9.25.12]) by mx1.freebsd.org (Postfix) with ESMTP id 1567E8FC0A; Wed, 19 Sep 2012 18:06:19 +0000 (UTC) X-AuditID: 1209190c-b7f286d000000ee3-a5-505a099b83b4 Received: from mailhub-auth-2.mit.edu ( [18.7.62.36]) by dmz-mailsec-scanner-1.mit.edu (Symantec Messaging Gateway) with SMTP id EE.FD.03811.B990A505; Wed, 19 Sep 2012 14:06:19 -0400 (EDT) Received: from outgoing.mit.edu (OUTGOING-AUTH.MIT.EDU [18.7.22.103]) by mailhub-auth-2.mit.edu (8.13.8/8.9.2) with ESMTP id q8JI6In8028479; Wed, 19 Sep 2012 14:06:19 -0400 Received: from multics.mit.edu (MULTICS.MIT.EDU [18.187.1.73]) (authenticated bits=56) (User authenticated as kaduk@ATHENA.MIT.EDU) by outgoing.mit.edu (8.13.6/8.12.4) with ESMTP id q8JI6Fra015864 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Wed, 19 Sep 2012 14:06:18 -0400 (EDT) Received: (from kaduk@localhost) by multics.mit.edu (8.12.9.20060308) id q8JI6FO3015657; Wed, 19 Sep 2012 14:06:15 -0400 (EDT) Date: Wed, 19 Sep 2012 14:06:15 -0400 (EDT) From: Benjamin Kaduk To: Doug Barton In-Reply-To: <5059194F.4090002@FreeBSD.org> Message-ID: References: <5059194F.4090002@FreeBSD.org> User-Agent: Alpine 1.10 (GSO 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrOIsWRmVeSWpSXmKPExsUixG6nojubMyrAYPp2bovXl76xWsx584HJ gcljxqf5LAGMUVw2Kak5mWWpRfp2CVwZd/beYCz4xF6x5d8GlgbGY2xdjJwcEgImEjNOPmCB sMUkLtxbDxTn4hAS2Mco8fr0OyhnA6PEye4tzBDOASaJyxevMkI4DYwS628cB5vFIqAtMeVN IxOIzSagIjHzzUagOAeHiICyxJWHbiBhZgF5if9XLjOBhIUF1CSeH8gDCXMCdf5ftBask1fA XuLd1MeMILaQgJbEs/0L2UFsUQEdidX7p7BA1AhKnJz5hAVipKXEv7W/WCcwCs5CkpqFJLWA kWkVo2xKbpVubmJmTnFqsm5xcmJeXmqRrqFebmaJXmpK6SZGUHhySvLsYHxzUOkQowAHoxIP r8KdiAAh1sSy4srcQ4ySHExKorw67FEBQnxJ+SmVGYnFGfFFpTmpxYcYJTiYlUR4f+yNDBDi TUmsrEotyodJSXOwKInzXk656S8kkJ5YkpqdmlqQWgSTleHgUJLgnckBNFSwKDU9tSItM6cE Ic3EwQkynAdo+AGQGt7igsTc4sx0iPwpRkUpcd58kIQASCKjNA+uF5Y+XjGKA70izNsDUsUD TD1w3a+ABjMBDa54EgYyuCQRISXVwOi6Rbpy84elkq9e6e7ftUSZty8wLjj1xx8hTq/KoNlB 12doCD77fqRCfP7T3GXswWdmTpTjPJWyYnm4+Kq6//NXTUgzkE0PaLn3y2LWHRE2tb9Xp0t2 /hcQ4X8S8nfdB7/kxZfrUmLerpJf5MTFlHXu7PIq1jXZbi2JRgVn5zCbsy4VvaR8+ZMSS3FG oqEWc1FxIgCE5KoS+gIAAA== Cc: freebsd-current@freebsd.org Subject: Re: squealing/whistling audio X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Sep 2012 18:06:20 -0000 On Tue, 18 Sep 2012, Doug Barton wrote: > Sometime in the last couple of months an old problem has resurfaced on > HEAD, a sort of squealing/whistling sound in the audio, even without > anything playing. The sound is similar to the wind whistling through > something. > > Before I blindly go off on a bisecting spree, does anyone have a > suggestion as to where I might look? It calls to mind this thread: http://lists.freebsd.org/pipermail/freebsd-current/2009-February/003608.html (with later followups http://lists.freebsd.org/pipermail/freebsd-current/2009-July/009839.html and http://lists.freebsd.org/pipermail/freebsd-current/2009-July/009850.html (and others?)) I had relief in my headphones with machdep.idle=spin, though that is only really useful when I am not paying my electricity bill... I agree with Matt that the noise is physically coming from analog leakage/crosstalk, and a software remedy will be something like disabling unused lines/pins. -Ben Kaduk