JohnYang1997 said: Basically yes. The damped response does not represent the response at human ear drum (what human hear) Less highs. Click to expand...

The standard IEC 60318-4 (former IEC 60711) Ear Simulator was designed in the early 1980s and mimics the input and transfer impedance of a human ear. While the input impedance was based on measurements on human subjects, the transfer impedance was based on the assumption that the ear canal is a simple cylindrical volume with a hard termination. Obviously the human ear canal is not a cylindrical cavity and the tympanic membrane is at an angle to the tapered ear canal. This questions the validity of the transfer impedance, particularly at high frequencies.



When the Ear Simulator was designed in the early 1980s the need for high frequency measurements above 10 kHz was limited. Within the hearing aid industry 8 kHz was considered adequate. Modern hearing aids and consumer electronics such as headphones require measurements at frequencies up to 20 kHz and beyond. When measuring with the Ear Simulator, the Device Under Test (DUT) is typically coupled by means of an ear canal ex- tension and a rubber pinna... Click to expand...

JohnYang1997 said: That's what b&k did. They stayed true to human.

The 60318-4 did not specify the amplitude of the peak at 13.5k. So gras just met the standard but actually the result change the frequency reaprese too much with shallow insertion earphones. Click to expand...

JohnYang1997 said: The main reason gras did that is for measurement consistency. It masks a lot of the inconsistency from different insert depth etc... Click to expand...

JohnYang1997 said: ...I believed that the n5005 measurements from harman slides is from bk's new hires head... Click to expand...

JohnYang1997 said: ...There are not much measurements done with bk's new head on the internet yet.

The comparison between gras new and old couplers can be seen from any measurements done by jude and 0db, earfi, speakerphone. Click to expand...

JohnYang1997 said: ...There are not much measurements done with bk's new head on the internet yet. Click to expand...

Here's GRAS's whitepaper on their HR simulators:The high Q, 1/2-wave resonance at 13.5 kHz is part of the specification that defines the main volume, but is actually outside of the standard's defined response tolerance (which stops at 10 kHz, as illustrated in Figure 3 in the whitepaper).Please read the entire whitepaper (linked above), but here's a short excerpt from it:In the whitepaper, you can see in Figure 7 and Figure 8 the response differences between a typical 60318-4 simulator and the newer simulator.Trivia: The "GR" in "GRAS," by the way, stands for Gunnar Rasmussen, who co-developed the original 60711 standard (now the 60318-4 standard). Gunnar Rasmussen left Brüel & Kjær and founded GRAS in 1994.In the whitepaper (linked above), you can see in Figure 4 and Figure 9 the comparison of the two (standard 60318-4 and the newer simulators), in terms of transfer impedance with varying canal lengths.I don't believe Harman has published any measurements from the Brüel & Kjær 5128 yet.If you listen to, you'll hear at around 21:55 that Sean and his team are now also using the newer GRAS ear simulators and anthropometric pinnae in their GRAS 45CA. And they also just recently acquired the Brüel & Kjær 5128 that you're referring to.We will likely also be doing measurements with the Brüel & Kjær 5128 in the future, so should be able to make some direct comparisons at some point.The original 60711 (60318-4) standard is nearly 40 years old. You'll continue to see changes and advances over time, as the needs for more accurate measurements and more accurate modeling of human perception beyond 10 kHz are becoming increasingly important.