Quicktime Player no audio on playback

I am using Quicktime player 10.4 version and when I try to play a movie file I get no sound. There is not even a sound icon in the playback control panel. I know the movies have sound because they work fine if I use Quicktime player 7. They files are .mov files. I am using OS 10.12.5 on an iMac intel i3 3.0 ghz mid 2010. I thought I had played movies before since upgrading my computer 6 months ago to Sierra but now I am not for sure. I was wondering if the recent upgrade Apple put out maybe is causing this issue?

Audio playback issue may have been triggered by the upgrade to Sierra depending on the Mac OS X version you upgraded from. Since Mavericks, QT X playback is directly supported by a "closed" codec AVFoundation structure embed while QT 7 is supported separately by the "classic" QT 7 structure embed which employs an "open" codec access as configured by the user. Since MOV file containers may store audio data which may or may not be "native" playback compatible with the AVFoundation or may employ audio settings that the AVFoundation may "dislike," it is possible that either is the source of your current issue. Thus, the first question usually asked is "What form of audio compression is used in the MOV file and/or at what sampling/data rate combination?"

I record these files on a HD DV camera that saves the movies in a .mov file format. It is an older Aiptek HD camcorder. I do not know what form of compression is used but the original manual says to open with Quicktime 7 to view the video on a pc computer. If I do a get info on the . mov file the only information I see is the dimension such as 720x480 or 1280x 720 and Codecs: H.264. Does that help? Also, this video camera is several years old.

Based on the information provided, I suspect the files are HDV encodes. (I.e., H.262/MPEG-2 video multiplexed with MPEG-1 Layer 2 audio.) Such files can be wrapped in either transport stream containers like TS, M2T and M2TS or program stream file containers like MOV, MPG or MPEG. Since the QT 7 Player only plays program stream files, use of the MOV file container was previously common. However, with the advent and development of QT X, it is more common to store such content in an MPEG container which is supported by the AVFoundation embed/QT X Player GUI and the "classic" QT embed/QT 7 Player GUI while the M2T (TS) container is only compatible with QT X Player and the AVFoundation. (I.e., this seems to be the current convention used by Compressor when exporting such content.)

Example:

On the other hand, an MOV file containing the same data plays fine in the QT 7 Player but converts video to H.264 with or without audio (or refuses to open at all) when attempting to play the file in the QT X Player depending on how the MOV file was multiplexed/created and/or copied to my hard drive. Unfortunately, without a source file on which to make tests, this explanation is merely guesswork at this time. (I.e., my current best guess is that the "Convert" embed is not currently programmed to properly recognize and transcode your data when in an MOV file container but the "legacy" QT 7 routines can.)

Frankly, based on your current results and the fact that you have QT 7 available, I would normally use QT 7 Pro to convert the data to an intermediate editing compression format (e.g., ProRes422/LPCM MOV file) which should be fully supported by all current Mac OS X/MacOS systems. If you don't have a key for "Pro" use, I would use an app like Compressor or a third-party converter like iSkysoft iMedia Converter Deluxe to achieve the same ends.

Do you get the same results importing the files into iMovie (or some other video editor) as you do copying the file directly to your HDD?

I downloaded iSkysoft and was able to convert a file (1/3 only without purchase) to a file that the new Quicktime 10.4 would play.

iSkysoft is representative of a class of third-party conversion apps available that are based on the FFmpeg open source codec project which can transcode most common modern and legacy compression formats in use today. I mentioned it by name only because I used it to convert the sample HDV content to ProRes422 on my system while answering your post. Almost any similar app will work as well so you should be able to easily find one that suits your individual needs, design fancy and pocketbook. HandBrake would work as well and is free but limits your output to MPEG-4 or H.264 video with AAC audio if you want the output to be totally compatible with all QT X/QT 7 based apps. I.e., H.264/AAC encoded media in MOV, M4P or M4V containers is normally used for distribution of your final content while ProRes422/LPCM MOV files have become the virtual default "poor man's intermediate codec" format (replacing AIC/LPCM MOV) for most users and is primarily used to archive and edit media content on all Mac OS X platforms since Mavericks, as well as, the latest MacOS Sierra. If all you require is the ability to play and trim your files for distribution, then HandBrake may be all you need here. However, if you plan to archive all of your camcorder files and edit them extensively in a video editor, then the ProRes422/LPCM MOV files would probably better suit your long-term requirements.

For the moment I will continue to use quicktime player 7 but I will need to purchase iSkysoft and convert all my files at some point.

Unlike the current QT 7/X GUIs, most dedicated conversion utilities, including HandBrake and the iSkysoft iMedia Converter Deluxe app, allow "batch" processing. That is, you can queue up a list of files along with their individual conversion settings and allow them to run while you are asleep, are off working and/or performing other tasks. This can be of great help if you have a very large number of files to be converted. (I.e., my system is on virtually 24/7 and is normally engaged in turning out "batch" conversions whenever I am not actively working on other projects since I am constantly updating and refining my iTunes managed video library.)