audio skills | Gareth Evans Portf 1

The most technical module of HNC Sound Production. I have spent my time learning, researching and developing my knowledge of audio in a classroom and studio setting.

Microphones

Microphone placement for piano. Ribbon condenser, to capture warmth and detail, a richness of sound. The piano is best moved to the centre of the room to capture the fullness of the sound and have each microphone placed in the stereo field. The string bed has three parts, the bass, middle and high, the ribbon microphones are pointed down into the strings. Long boom stands are used to lean over from the back and have the microphones perpendicular to the string bed. The ribbons are figure of eight polar patterns, the null of the pattern suited to cancelling out bleed and focusing the pickup of sound to the source. When using two microphones to capture a stereo image, it is important that they are a stereo matched pair, in that the level of each microphone corresponds to the other.

The Sennheiser MD421 is a dynamic microphone, which can handle high sound pressure levels (SPL) which are placed at the bottom of the piano, where the bass sounds will be most prominent. Dynamic microphones are very rugged and are typically cardioid/ hyper cardioid.

Microphone choice varies with each project, below is a link to a document for a recording project very different to the studio setting. I had to investigate and choose the appropriate microphone for the project.

Proposol for Recording Project

Room Acoustic Analysis

I was tasked to provide a written/graphical response to questions on two case studies presented. Each case study was based on an enclosed space. Below is an investigation of the acoustic properties of each enclosed space.

Reverberation is the persistent reflection of a sound source as it travels through a space, before dissipating to an inaudible volume. The length and time of the reverberation can be affected by factors such as size of the space, the type of surfaces and the density of these surfaces. A large space such as hall or cathedral with many hard surfaces, stone or tile, will result in a long reverberation, whilst a small room with carpeting and soft furnishings will have a muted reverberation. Volume could be an independent factor in reverberation as two spaces could have different sound absorption properties.

Sound consists of oscillating waves that propagate through the air (takustik.com, 2023). The sound absorption properties of the materials will affect this. Eastlake 1 has been treated with a dense but porous material known as Rockwool, with a high sound absorption coefficient.

Figure 1 https://www.audiosciencereview.com/forum/index.php?attachments/absorption-coefficients-of-rockwool-slabs-v2-2019-pdf.110315/

When the sound hits the Rockwool, its energy is absorbed into the material. Frequencies from low, 100Hz. to the higher end 5kHz will be absorbed dependent on the density of the material.

Eastlake 1 has been acoustically treated to absorb sound and results in a low reverberation time.

Figure 2 Impulse Response of Eastlake 1

The RT60 time of Eastlake 1 is 0.223 a short reverberation time, resulting in a clear critical listening room for mixing and mastering. Moreover, the frequency response of the space is shown to be flat from a wide range of frequencies, bass mids and highs, as evidenced by Figure 3

Figure 3 Frequency Response Graph. Eastlake 1 green, Room 440 blue

In contrast, Room 440 has a longer RT60 time, the material of the wall being breezeblock, which possesses poor sound absorption qualities, compounded with being painted. This amplifies the sound reflections and reverberation, leading to a build up of frequencies as seen in figure 3. The floor will have to be considered, the reflective nature of the linoleum adding to the frequency response of the room.

Figure 4 – Room 440 Figure 5 - Eastlake 1

Eastlake 1 has been treated to bring a clarity to the source material that is being mix or mastered in that space. There is no influence on the sound, what is produced by the monitoring system is the transparent image of the source. These qualities are crucial to a critical listening environment. Surfaces have been treated with appropriate sound absorption materials but also the shape of the space has been designed to minimise reflections (figure 5) and standing sound waves, where the sound is reflected back along its own path. These standing waves can combine in constructive and destructive interference dependent on phase. A attenuation in decibel occurs when the sound wave is out of phase, known as cancellation, whereas an in phase sound wave increases the amplitude. Defects of the space will come from hard surfaces such as the mixing console, furniture and glass windows.

Room 440 (figure 4) has a rectangular shape, the walls, floor and roof are parallel surfaces with hard, reflective materials, leading to an increased reverberation and a higher chance of standing waves occurring. The length of the room is a factor in the RT60 time, a reverberation often occurs in a small room with height, width, and length dimensions of approximately 17 meters or less. https://www.cemca.org/ckfinder/userfiles/files/5_Lesson-04_STUDIO_ACOUSTICS.pdf

Eastlake 1 has been treated with acoustic panels, the angles of the walls are not parallel. There is a lack of diffusers in the environment, these could be placed in the space to further break up the sound. Diffusers are acoustical boundaries that reflect the sound wave back at various angles that are wider than the original incident angle (thereby breaking up the energy destructive standing waves).( Huber, D.M. et al. ,2024, p84)

Room 440 could benefit from Rockwool absorption panels, although the space is small as it is. Covering reflective surfaces with diffusers and installing bass traps in the 90 degree corners, finishing with thick carpeting on the floor.

The portable test system yielded accurate results for the duration of the tests. Improvements could be an upgrade of equipment. The MM-1 is a class 1 measurement microphone, the data sheet shows a flat frequency response until it reaches 5kHz.

Figure 6 Frequency response of MM-1

My investigation of Class 1 microphones has led me to the Earthworks M50, which has a flat frequency response up to 50kHz, although would this be unnecessary for human hearing in a mix or mastering environment?

Figure 7 Frequency response of M50

Other factors to consider in the measurement environment would be temperature of the space, as this can affect the nature of the sound waves as they travel through listening environment. Creating a more stable temperature could yield more accurate results. Placement of the equipment, the distance between microphone and sound source.

Figure 8 - Room analysis and measurement equipment

References

Huber, D.M. et al. (2024) Modern recording techniques : a practical guide to modern music production. Tenth edition. New York, NY: Routledge.

https://www.audiosciencereview.com/forum/index.php?attachments/absorption-coefficients-of-rockwool-slabs-v2-2019-pdf.110315/(Accessed 14/05/2025).

https://www.cemca.org/ckfinder/userfiles/files/5_Lesson-04_STUDIO_ACOUSTICS.pdf(Accessed 14/05/2025).

FREQUENCY RANGES (2023) FREQUENCY RANGES. Available at: https://takustik.com/magazine/frequency-ranges/ (Accessed 14/05/2025).

Schematic Diagram of Eastlake 1

Schematic diagram of Eastlake 1. It is a plan or technical drawing of an electronic system. Listing components and connections for a studio setup. Seen from a birds eyes perspective, it is not to scale. Listed here is the live room, control room and machine room, which are the three key rooms for a recording studio

Ticket pass for use of the studios. I think of it as a driving licence for a mixing desk. I had to study and research on how to use the mixing desk and its features, from seemingly basic functions such as headphones to more complex routing on the patch bay. Now I have this training, I am able to approach a mixing console with confidence and apply my creative processes using the technical features of a broad set of consoles.