Have you ever wanted to know how something you were using works? This post deals with a bit of a fun diversion where my curiosity about a virtual speaker simulation tool led me to do a patent search to do just that.
When I was studying mechanical engineering, I was fascinated with sound. I had been a musician since third grade and a wannabe audiophile. After my first co-op in college, I finally had enough money to splurge on a surround sound stereo and speakers. I spent weeks reading up on the subject and finally went to the local stereo shop on High Street in Columbus with a stack of CDs and auditioned speakers. Those trusty speakers from college went to law school and eventually wound up in my living room at my house where they occupied pretty significant real estate. In an effort to de-clutter during Covid, I decided to replace my old fashioned tower speakers with in-ceiling speakers. Being in a pandemic, I turned to Crutchfield, an online mail order company that offers a wide array of audio products, and an interesting virtual audition tool that I had never heard before.
To help you compare and select speakers Crutchfield allows you to load up to four speakers into this tool and virtually audition them using headphones. The tool promises to recreate the sound of the speaker in your house using your headphones. When you load the tool, you identify the type of headphones that you are using and then listen to a stock list of audio tracks while switching between speakers. The tool simulates the differences in sound and volume level based on the frequency response, resistance and efficiency of each speaker. To get more of an apples to apples comparison of sound, it also will compensate for the resistance and efficiency differences to make the volume uniform as you switch between speakers.
Having no frame of reference I didn't know how accurate the test would be, but in listening, I found speakers that I definitely didn't like and began to recognize sound characteristics of certain brands. I spent an inordinate amount of time trying different speakers and using the simulator with different headphones to see if that would make a difference. I began noticing that guitars and vocals seemed a little more open with some speakers and pinched with others. At one point, a speaker with particularly good low frequency response revealed base sounds in one track that I hadn't even heard when simulating another speaker. Even if not true to the sound of the speakers in my house, the ability of the tool to demonstrate varying characteristics between speakers made me want to know how it worked.
The website mentioned that it was a patented technology giving me my backstage pass. This is one of the promises of the patent system. The patent owner receives exclusive rights for a limited time in exchange for public disclosure of their innovation. I did some quick patent searching and found several patents owned by Crutchfield relating to this technology including U.S. Patent 7,899,656. What I learned from this patent is that Crutchfield's founder originally wanted to be able to provide accurate simulations of various pieces of audio equipment in a store environment but the environment was not necessarily representative of the user's home.
The starting point was to be able to isolate the characteristics of the speaker and simulate its performance irrespective of its environment. This concept eventually extended to a virtual environment relying on the user having a known set of headphones. Essentially, Crutchfield played the reference tracks through the actual speakers in an anechoic chamber with a high quality reference microphone recording the digital signature (transfer function) of each speaker. Then to account for the characteristics of the headphones used to play the sound for the user, they performed the same process for most of the headphones on the market and were able to filter out the influences created by the headphones.
As mentioned, the speakers displayed noticeable differences when compared with the tool, and after I settled on a few that I liked, I ordered them to see how the virtual sound compared to real thing. It was surprisingly accurate! If anything, the sound quality is better at home, but the same sound characteristics captured in the simulation were evident at home. For example, during the test I was surprised to find that I did not like the sound of the in ceiling speakers with a built in box compared to open ceiling speaker from the same manufacturer. The engineer in me struggled with this because having a dedicated enclosure as part of the speaker should ensure consistent sound. However, during the test, the sound from these seemed a little too tight and slightly muffled. I bought one of these to compare to the open speaker. I tried them in open air and in the ceiling and the sound matched what I had heard during the simulation.
Kudos to Crutchfield for creating such a useful technology, and sharing it through the patent system.
The CueCards takeaway from this is that patent searching can be a useful tool to gain insight into existing technologies. From a research and development standpoint, patent searching helps identify whether a development is patentable and whether it will infringe upon existing rights. More sophisticated searching may be used to invalidate existing patents or identify patent voids or white spaces where targeted development can provide significant exclusivity. If you have searching questions or just want to talk speakers, feel free to reach out or comment below.