Telecommunications Tech Blog February 2014
Call Quality: An Easy Way to Hear How Your Phone Sounds
By Mike Sandman •
Call quality is one of the
biggest issues with VoIP phone calls. Maybe the biggest?
A big problem is when the Echo
Canceller in the phone or in the station port / CO line interface is turned up
too high, causing a clicking / ticking / staticky sound that you generally don't
hear on the end making the call.
I take calls all day from companies
all over the country and am appalled at the quality of many of the calls. The
biggest problem is that the guys calling me don't even know!
As long as our own voice sounds OK in
our handset (called sidetone) it's easy to assume we sound OK to the person at the
If you're using VoIP you can't assume
that. But there is an easy way to find out how you sound.
The Test Call (
http://thetestcall.blogspot.com ) operates
a free test number that anybody can call (from any kind of line) to see how they sound by letting you
talk - and then playing back your voice. He has the service available through
several SIP providers which is important since one route may work OK, and the
other not so good.
The Test Call will
record your voice until you hit #, then play it back.
It also reads back your Caller
ID, does an Echo Test which gives you an idea of the latency (delay) on that
and allows you to do several other neat tests including check to see how the
Touch Tone digits are received by his system (sometimes a problem with SIP!).
These are the two phone numbers he
provides (they don't have unlimited numbers in the hunt, so you may get a busy
40-VOIP-INFO (408-647-4636) Google
number (A service where you can get a free Washington state incoming
phone number to use with your SIP device (
The Menu Options are the same (try both to make sure their end is working
if you hear a problem!):
- (Default) Record and Playback, the most requested feature.
the # key to stop the recording and listen to how you sound.
- DTMF testing - Enter a string of DTMF keys and
press # to get a read out
- Real time Echo test
- Playback Music on Hold
- Test Conference Bridge
- 0-4Khz audio sweep
- Caller ID Readback (like ANI)
Note that the Caller ID you get may be just
the main number of the company depending on how your trunks and phone system are
Bob's 40-VOIP-INFO number uses Google
Voice. He mentioned that even though Google Voice is changing the way their
service works on May 15th, he's pretty sure the way he has it setup it will
If it doesn't work he says there will
be a recording on the number telling you how to reach his machine. He also
provides service updates on Twitter:
Google Voice is changing to Hangouts (I
think?). It was possible to use a Google Voice number on some VoIP phone
systems, or use it in apps, but that ends on May 15th if Google doesn't change
Bob also has a bunch of SIP URIs on his
page to make the test call through several different VoIP SIP providers. You
would just enter the URI (starting with sip:) into a VoIP phone that would let
you do that, like the free X-Lite Windows softphone from CounterPath:
Doing a tracert from the same network (like:
tracert sip.linphone.org) after testing with a URI
lets you see where the server is (like across the country or even in another
country) and how long it takes the packets to get there (which may be the reason
the call sounds bad?).
Tracing route to sip.linphone.org [126.96.36.199]
over a maximum of 30 hops:
1 <1 ms <1 ms 1 ms 192.168.1.1
2 13 ms 9 ms 9 ms atm001.e40.chi.megapath.net [188.8.131.52]
3 14 ms 9 ms 9 ms ge-2-0-0-10.c00.chi.bb.megapath.net [184.108.40.206]
4 16 ms 9 ms 9 ms ge-0-1-2-0.chcgilgb-mxc1.bb.megapath.net [220.127.116.11]
5 27 ms 27 ms 27 ms ae4-0.nycmny83-mxc1.bb.megapath.net [18.104.22.168]
6 26 ms 27 ms 26 ms ge-3-1-0-0.c00.nyp.bb.megapath.net [22.214.171.124]
7 32 ms * 26 ms eqx.ny.ovh.net [126.96.36.199]
8 * 46 ms * nwk-1-6k.nj.us [188.8.131.52]
9 * *
* Request timed out.
10 100 ms 102 ms 102 ms rbx-g1-a9.fr.eu [184.108.40.206]
11 * 99 ms * rbx-1-6k.fr.eu [220.127.116.11]
12 101 ms 99 ms 102 ms rbx-60-m1.fr.eu [18.104.22.168]
13 101 ms 99 ms 102 ms sip.linphone.org [22.214.171.124]
Bob says you can press 0 on his machine to leave him a
voicemail/comment/problem report. He says feedback has been very helpful to
improve the system.
Bob also says that anyone with a PSTN/SIP
gateway (or a VoIP service provider) could point a DID they own to a direct SIP
URI at his service. He says he doesn't publish that information on the
public page, but he's happy to let folks direct a number they control/own to his
He says "If they are debugging their own
PSTN/SIP gateways, it might be handy to have an independent SIP service that
will try really hard to answer the test call."
Contact Bob at:
The Test Call should be
the first thing you use when diagnosing call quality problems. Allowing you to
reach his machine through various SIP providers makes this one of the most
important tools you can use today.
Keep in mind that if Bob's system is
down or screwed up, all of his numbers will have problems until he fixes it.
Bob's service is totally free, but
you may want to purchase some "Erlangs" from his page to support his service?
It's worth its weight in gold!